Critiques and Addresses
by
Thomas Henry Huxley
Part 2 out of 6
effect already exists. The Science and Art Department, the operations
of which have already attained considerable magnitude, not only offers
to examine and pay the results of such examination in elementary
science and art, but it provides what is still more important, viz.
a means of giving children of high natural ability, who are just as
abundant among the poor as among the rich, a helping hand. A good old
proverb tells us that "One should not take a razor to cut a block:"
the razor is soon spoiled, and the block is not so well cut as it
would be with a hatchet. But it is worse economy to prevent a possible
Watt from being anything but a stoker, or to give a possible Faraday
no chance of doing anything but to bind books. Indeed, the loss in
such cases of mistaken vocation has no measure; it is absolutely
infinite and irreparable. And among the arguments in favour of the
interference of the State in education, none seems to be stronger
than this--that it is the interest of every one that ability should be
neither wasted, nor misapplied, by any one; and, therefore, that every
one's representative, the State, is necessarily fulfilling the wishes
of its constituents when it is helping the capacities to reach their
proper places.
It may be said that the scheme of education here sketched is too large
to be effected in the time during which the children will remain at
school; and, secondly, that even if this objection did not exist, it
would cost too much.
I attach no importance whatever to the first objection until the
experiment has been fairly tried. Considering how much catechism,
lists of the kings of Israel, geography of Palestine, and the like,
children are made to swallow now, I cannot believe there will be any
difficulty in inducing them to go through the physical training, which
is more than half play; or the instruction in household work, or in
those duties to one another and to themselves, which have a daily and
hourly practical interest. That children take kindly to elementary
science and art no one can doubt who has tried the experiment
properly. And if Bible-reading is not accompanied by constraint and
solemnity, as if it were a sacramental operation, I do not believe
there is anything in which children take more pleasure. At least I
know that some of the pleasantest recollections of my childhood are
connected with the voluntary study of an ancient Bible which belonged
to my grandmother. There were splendid pictures in it, to be sure; but
I recollect little or nothing about them save a portrait of the
high priest in his vestments. What come vividly back on my mind are
remembrances of my delight in the histories of Joseph and of David;
and of my keen appreciation of the chivalrous kindness of Abraham in
his dealings with Lot. Like a sudden flash there returns back upon
me, my utter scorn of the pettifogging meanness of Jacob, and my
sympathetic grief over the heartbreaking lamentation of the cheated
Esau, "Hast thou not a blessing for me also, O my father?" And I see,
as in a cloud, pictures of the grand phantasmagoria of the Book of
Revelation.
I enumerate, as they issue, the childish impressions which come
crowding out of the pigeon-holes in my brain, in which they have lain
almost undisturbed for forty years. I prize them as an evidence that a
child of five or six years old, left to his own devices, may be deeply
interested in the Bible, and draw sound moral sustenance from it. And
I rejoice that I was left to deal with the Bible alone; for if I had
had some theological "explainer" at my side, he might have tried,
as such do, to lessen my indignation against Jacob, and thereby have
warped my moral sense for ever; while the great apocalyptic spectacle
of the ultimate triumph of right and justice might have been turned to
the base purposes of a pious lampooner of the Papacy.
And as to the second objection--costliness--the reply is, first, that
the rate and the Parliamentary grant together ought to be enough,
considering that science and art teaching is already provided
for; and, secondly, that if they are not, it may be well for the
educational parliament to consider what has become of those endowments
which were originally intended to be devoted, more or less largely, to
the education of the poor.
When the monasteries were spoiled, some of their endowments were
applied to the foundation of cathedrals; and in all such cases it was
ordered that a certain portion of the endowment should be applied to
the purposes of education. How much is so applied? Is that which may
be so applied given to help the poor, who cannot pay for education, or
does it virtually subsidize the comparatively rich, who can? How
are Christ's Hospital and Alleyn's foundation securing their right
purposes, or how far are they perverted into contrivances for
affording relief to the classes who can afford to pay for education?
How--But this paper is already too long, and, if I begin, I may find
it hard to stop asking questions of this kind, which after all are
worthy only of the lowest of Radicals.
III.
ON MEDICAL EDUCATION.
(AN ADDRESS TO THE STUDENTS OF THE FACULTY OF MEDICINE IN UNIVERSITY
COLLEGE, LONDON, MAY 18, 1870, ON THE OCCASION OF THE DISTRIBUTION OF
PRIZES FOR THE SESSION.)
It has given me sincere pleasure to be here to-day, at the desire of
your highly respected President and the Council of the College. In
looking back upon my own past, I am sorry to say that I have found
that it is a quarter of a century since I took part in those hopes and
in those fears by which you have all recently been agitated, and which
now are at an end. But, although so long a time has elapsed since
I was moved by the same feelings, I beg leave to assure you that my
sympathy with both victors and vanquished remains fresh--so fresh,
indeed, that I could almost try to persuade myself that, after all, it
cannot be so very long ago. My business during the last hour, however,
has been to show that sympathy with one side only, and I assure you
I have done my best to play my part heartily, and to rejoice in the
success of those who have succeeded. Still, I should like to remind
you at the end of it all, that success on an occasion of this kind,
valuable and important as it is, is in reality only putting the foot
upon one rung of the ladder which leads upwards; and that the rung of
a ladder was never meant to rest upon, but only to hold a man's foot
long enough to enable him to put the other somewhat higher. I trust
that you will all regard these successes as simply reminders that your
next business is, having enjoyed the success of the day, no longer to
look at that success, but to look forward to the next difficulty
that is to be conquered. And now, having had so much to say to the
successful candidates, you must forgive me if I add that a sort of
undercurrent of sympathy has been going on in my mind all the time for
those who have not been successful, for those valiant knights who have
been overthrown in your tourney, and have not made their appearance in
public. I trust that, in accordance with old custom, they, wounded and
bleeding, have been carried off to their tents, to be carefully tended
by the fairest of maidens; and in these days, when the chances are
that every one of such maidens will be a qualified practitioner,
I have no doubt that all the splinters will have been carefully
extracted, and that they are now physically healed. But there may
remain some little fragment of moral or intellectual discouragement,
and therefore I will take the liberty to remark that your chairman
to-day, if he occupied his proper place, would be among them. Your
chairman, in virtue of his position, and for the brief hour that he
occupies that position, is a person of importance; and it may be some
consolation to those who have failed if I say, that the quarter of a
century which I have been speaking of, takes me back to the time
when I was up at the University of London, a candidate for honours in
anatomy and physiology, and when I was exceedingly well beaten by my
excellent friend Dr. Ransom, of Nottingham. There is a person here
who recollects that circumstance very well. I refer to your venerated
teacher and mine, Dr. Sharpey. He was at that time one of the
examiners in anatomy and physiology, and you may be quite sure that,
as he was one of the examiners, there remained not the smallest doubt
in my mind of the propriety of his judgment, and I accepted my defeat
with the most comfortable assurance that I had thoroughly well earned
it. But, gentlemen, the competitor having been a worthy one, and
the examination, a fair one, I cannot say that I found in that
circumstance anything very discouraging. I said to myself, "Never
mind; what's the next thing to be done?" And I found that policy of
"never minding" and going on to the next thing to be done, to be the
most important of all policies in the conduct of practical life. It
does not matter how many tumbles you have in this life, so long as you
do not get dirty when you tumble; it is only the people who have to
stop to be washed and made clean, who must necessarily lose the race.
And I can assure you that there is the greatest practical benefit
in making a few failures early in life. You learn that which is of
inestimable importance--that there are a great many people in the
world who are just as clever as you are. You learn to put your trust,
by and by, in an economy and frugality of the exercise of your powers,
both moral and intellectual; and you very soon find out, if you have
not found it out before, that patience and tenacity of purpose are
worth more than twice their weight of cleverness. In fact, if I were
to go on discoursing on this subject, I should become almost eloquent
in praise of non-success; but, lest so doing should seem, in any way,
to wither well-earned laurels, I will turn from that topic, and ask
you to accompany me in some considerations touching another subject
which has a very profound interest for me, and which I think ought to
have an equally profound interest for you.
I presume that the great majority of those whom I address propose to
devote themselves to the profession of medicine; and I do not doubt,
from the evidences of ability which have been given to-day, that
I have before me a number of men who will rise to eminence in that
profession, and who will exert a great and deserved influence upon
its future. That in which I am interested, and about which I wish to
speak, is the subject of medical education, and I venture to speak
about it for the purpose, if I can, of influencing you, who may have
the power of influencing the medical education of the future. You may
ask, by what authority do I venture, being a person not concerned in
the practice of medicine, to meddle with that subject? I can only tell
you it is a fact, of which a number of you I dare say are aware by
experience (and I trust the experience has no painful associations),
that I have been for a considerable number of years (twelve or
thirteen years to the best of my recollection) one of the examiners in
the University of London. You are further aware that the men who
come up to the University of London are the picked men of the medical
schools of London, and therefore such observations as I may have
to make upon the state of knowledge of these gentlemen, if they be
justified, in regard to any faults I may have to find, cannot be held
to indicate defects in the capacity, or in the power of application of
those gentlemen, but must be laid, more or less, to the account of the
prevalent system of medical education. I will tell you what has struck
me--but in speaking in this frank way, as one always does about the
defects of one's friends, I must beg you to disabuse your minds of
the notion that I am alluding to any particular school, or to any
particular college, or to any particular person; and to believe that
if I am silent when I should be glad to speak with high praise, it is
because that praise would come too close to this locality. What has
struck me, then, in this long experience of the men best instructed in
physiology from the medical schools of London, is (with the many and
brilliant exceptions to which I have referred), taking it as a whole,
and broadly, the singular unreality of their knowledge of physiology.
Now, I use that word "unreality" advisedly: I do not say "scanty;" on
the contrary, there is plenty of it--a great deal too much of it--but
it is the quality, the nature of the knowledge, which I quarrel with.
I know I used to have--I don't know whether I have now, but I had once
upon a time--a bad reputation among students for setting up a very
high standard of acquirement, and I dare say you may think that the
standard of this old examiner, who happily is now very nearly an
extinct examiner, has been pitched too high. Nothing of the kind, I
assure you. The defects I have noticed, and the faults I have to find,
arise entirely from the circumstance that my standard is pitched too
low. This is no paradox, gentlemen, but quite simply the fact.
The knowledge I have looked for was a real, precise, thorough, and
practical knowledge of fundamentals; whereas that which the best of
the candidates, in a large proportion of cases, have had to give me
was a large, extensive, and inaccurate knowledge of superstructure;
and that is what I mean by saying that my demands went too low,
and not too high. What I have had to complain of is, that a large
proportion of the gentlemen who come up for physiology to the
University of London do not know it as they know their anatomy, and
have not been taught it as they have been taught their anatomy. Now, I
should not wonder at all if I heard a great many "No, noes" here; but
I am not talking about University College; as I have told you before,
I am talking about the average education of medical schools. What I
have found, and found so much reason to lament, is, that while anatomy
has been taught as a science ought to be taught, as a matter of
autopsy, and observation, and strict discipline; in a very large
number of cases, physiology has been taught as if it were a mere
matter of books and of hearsay. I declare to you, gentlemen, that
I have often expected to be told, when I have been asked a question
about the circulation of the blood, that Professor Breitkopf is
of opinion that it circulates, but that the whole thing is an open
question. I assure you that I am hardly exaggerating the state of mind
on matters of fundamental importance which I have found over and over
again to obtain, among gentlemen coming up to that picked examination
of the University of London. Now, I do not think that is a desirable
state of things. I cannot understand why physiology should not be
taught--in fact, you have here abundant evidence that it can be
taught--with the same definiteness and the same precision as anatomy
is taught. And you may depend upon this, that the only physiology
which is to be of any good whatever in medical practice, or in its
application to the study of medicine, is that physiology which a man
knows of his own knowledge; just as the only anatomy which would be
of any good to the surgeon is the anatomy which he knows of his own
knowledge. Another peculiarity I have found in the physiology which
has been current, and that is, that in the minds of a great many
gentlemen it has been supplanted by histology. They have learnt a
great deal of histology, and they have fancied that histology and
physiology are the same things. I have asked for some knowledge of the
physics and the mechanics and the chemistry of the human body, and I
have been met by talk about cells. I declare to you I believe it will
take me two years, at least, of absolute rest from the business of
an examiner to hear the word "cell," "germinal matter," or "carmine,"
without a sort of inward shudder.
Well, now, gentlemen, I am sure my colleagues in this examination will
bear me out in saying that I have not been exaggerating the evils and
defects which are current--have been current--in a large quantity
of the physiological teaching, the results of which come before
examiners. And it becomes a very interesting question to know how all
this comes about, and in what way it can be remedied. How it comes
about will be perfectly obvious to any one who has considered the
growth of medicine. I suppose that medicine and surgery first began
by some savage, more intelligent than the rest, discovering that a
certain herb was good for a certain pain, and that a certain pull,
somehow or other, set a dislocated joint right. I suppose all things
had their humble beginnings, and medicine and surgery were in the same
condition. People who wear watches know nothing about watchmaking. A
watch goes wrong and it stops; you see the owner giving it a shake,
or, if he is very bold, he opens the case, and gives the balance-wheel
a turn. Gentlemen, that is empirical practice, and you know what are
the results upon the watch. I should think you can divine what are the
results of analogous operations upon the human body. And because men
of sense very soon found that such were the effects of meddling with
very complicated machinery they did not understand, I suppose the
first thing, as being the easiest, was to study the nature of the
works of the human watch, and the next thing was to study the way the
parts worked together, and the way the watch worked. Thus, by degrees,
we have had growing up our body of anatomists, or knowers of the
construction of the human watch, and our physiologists, who know how
the machine works. And just as any sensible man, who has a valuable
watch, does not meddle with it himself, but goes to some one who has
studied watchmaking, and understands what the effect of doing this
or that may be; so, I suppose, the man who, having charge of that
valuable machine, his own body, wants to have it kept in good order,
comes to a professor of the medical art for the purpose of having it
set right, believing that, by deduction from the facts of structure
and from the facts of function, the physician will divine what may be
the matter with his bodily watch at that particular time, and what may
be the best means of setting it right. If that may be taken as a
just representation of the relation of the theoretical branches of
medicine--what we may call the institutes of medicine, to use an old
term--to the practical branches, I think it will be obvious to you
that they are of prime and fundamental importance. Whatever tends to
affect the teaching of them injuriously must tend to destroy and
to disorganize the whole fabric of the medical art. I think every
sensible man has seen this long ago; but the difficulties in the way
of attaining good teaching in the different branches of the theory, or
institutes, of medicine are very serious. It is a comparatively
easy matter--pray mark that I use the word "comparatively"--it is a
comparatively easy matter to learn anatomy and to teach it; it is a
very difficult matter to learn physiology and to teach it. It is a
very difficult matter to know and to teach those branches of physics
and those branches of chemistry which bear directly upon physiology;
and hence it is that, as a matter of fact, the teaching of physiology,
and the teaching of the physics and the chemistry which bear upon it,
must necessarily be in a state of relative imperfection; and there is
nothing to be grumbled at in the fact that this relative imperfection
exists. But is the relative imperfection which exists only such as
is necessary, or is it made worse by our practical arrangements? I
believe--and if I did not so believe I should not have troubled you
with these observations--I believe it is made infinitely worse by
our practical arrangements, or rather, I ought to say, our very
unpractical arrangements. Some very wise man long ago affirmed that
every question, in the long run, was a question of finance; and there
is a good deal to be said for that view. Most assuredly the question
of medical teaching is, in a very large and broad sense, a question of
finance. What I mean is this: that in London the arrangements of the
medical schools, and the number of them, are such as to render it
almost impossible that men who confine themselves to the teaching
of the theoretical branches of the profession should be able to make
their bread by that operation; and, you know, if a man cannot make his
bread, he cannot teach--at least his teaching comes to a speedy end.
That is a matter of physiology. Anatomy is fairly well taught, because
it lies in the direction of practice, and a man is all the better
surgeon for being a good anatomist. It does not absolutely interfere
with the pursuits of a practical surgeon if he should hold a Chair
of Anatomy--though I do not for one moment say that he would not be a
better teacher if he did not devote himself to practice. (Applause.)
Yes, I know exactly what that cheer means, but I am keeping as
carefully as possible from any sort of allusion to Professor Ellis.
But the fact is, that even human anatomy has now grown to be so large
a matter, that it takes the whole devotion of a man's life to put the
great mass of knowledge upon that subject into such a shape that it
can be teachable to the mind of the ordinary student. What the student
wants in a professor is a man who shall stand between him and the
infinite diversity and variety of human knowledge, and who shall
gather all that together, and extract from it that which is capable
of being assimilated by the mind. That function is a vast and an
important one, and unless, in such subjects as anatomy, a man is
wholly free from other cares, it is almost impossible that he can
perform it thoroughly and well. But if it be hardly possible for a man
to pursue anatomy without actually breaking with his profession, how
is it possible for him to pursue physiology?
I get every year those very elaborate reports of Henle and
Meissner--volumes of, I suppose, 400 pages altogether--and they
consist merely of abstracts of the memoirs and works which have been
written on Anatomy and Physiology--only abstracts of them! How is
a man to keep up his acquaintance with all that is doing in the
physiological world--in a world advancing with enormous strides every
day and every hour--if he has to be distracted with the cares of
practice? You know very well it must be impracticable to do so. Our
men of ability join our medical schools with an eye to the future.
They take the Chairs of Anatomy or of Physiology; and by and by they
leave those Chairs for the more profitable pursuits into which they
have drifted by professional success, and so they become clothed,
and physiology is bare. The result is, that in those schools in which
physiology is thus left to the benevolence, so to speak, of those
who have no time to look to it, the effect of such teaching comes
out obviously, and is made manifest in what I spoke of just now--the
unreality, the bookishness of the knowledge of the taught. And if this
is the case in physiology, still more must it be the case in those
branches of physics which are the foundation of physiology; although
it may be less the case in chemistry, because for an able chemist a
certain honourable and independent career lies in the direction of
his work, and he is able, like the anatomist, to look upon what he
may teach to the student as not absolutely taking him away from his
bread-winning pursuits.
But it is of no use to grumble about this state of things unless
one is prepared to indicate some sort of practical remedy. And I
believe--and I venture to make the statement because I am wholly
independent of all sorts of medical schools, and may, therefore, say
what I believe without being supposed to be affected by any personal
interest--but I say I believe that the remedy for this state of
things, for that imperfection of our theoretical knowledge which keeps
down the ability of England at the present time in medical matters,
is a mere affair of mechanical arrangement; that so long as you have
a dozen medical schools scattered about in different parts of the
metropolis, and dividing the students among them, so long, in all the
smaller schools at any rate, it is impossible that any other state of
things than that which I have been depicting should obtain. Professors
must live; to live they must occupy themselves with practice, and
if they occupy themselves with practice, the pursuit of the abstract
branches of science must go to the wall. All this is a plain and
obvious matter of common-sense reasoning. I believe you will never
alter this state of things until, either by consent or by _force
majeure_--and I should be very sorry to see the latter applied--but
until there is some new arrangement, and until all the theoretical
branches of the profession, the institutes of medicine, are taught in
London in not more than one or two, or at the outside three, central
institutions, no good will be effected. If that large body of men, the
medical students of London, were obliged in the first place to get a
knowledge of the theoretical branches of their profession in two or
three central schools, there would be abundant means for maintaining
able professors--not, indeed, for enriching them, as they would be
able to enrich themselves by practice--but for enabling them to make
that choice which such men are so willing to make; namely, the choice
between wealth and a modest competency, when that modest competency
is to be combined with a scientific career, and the means of advancing
knowledge. I do not believe that all the talking about, and tinkering
of, medical education will do the slightest good until the fact
is clearly recognized, that men must be thoroughly grounded in the
theoretical branches of their profession, and that to this end the
teaching of those theoretical branches must be confined to two or
three centres.
Now let me add one other word, and that is, that if I were a despot, I
would cut down these branches to a very considerable extent. The next
thing to be done beyond that which I mentioned just now, is to go
back to primary education. The great step towards a thorough medical
education is to insist upon the teaching of the elements of the
physical sciences in all schools, so that medical students shall not
go up to the medical colleges utterly ignorant of that with which they
have to deal; to insist on the elements of chemistry, the elements of
botany, and the elements of physics being taught in our ordinary
and common schools, so that there shall be some preparation for
the discipline of medical colleges. And, if this reform were once
effected, you might confine the "Institutes of Medicine" to physics
as applied to physiology--to chemistry as applied to physiology--to
physiology itself, and to anatomy. Afterwards, the student, thoroughly
grounded in these matters, might go to any hospital he pleased for
the purpose of studying the practical branches of his profession. The
practical teaching might be made as local as you like; and you
might use to advantage the opportunities afforded by all these
local institutions for acquiring a knowledge of the practice of the
profession. But you may say: "This is abolishing a great deal; you are
getting rid of botany and zoology to begin with." I have not a doubt
that they ought to be got rid of, as branches of special medical
education; they ought to be put back to an earlier stage, and made
branches of general education. Let me say, by way of self-denying
ordinance, for which you will, I am sure, give me credit, that I
believe that comparative anatomy ought to be absolutely abolished.
I say so, not without a certain fear of the Vice-Chancellor of the
University of London who sits upon my left. But I do not think the
charter gives him very much power over me; moreover, I shall soon come
to an end of my examinership, and therefore I am not afraid, but shall
go on to say what I was going to say, and that is, that in my belief
it is a downright cruelty--I have no other word for it--to require
from gentlemen who are engaged in medical studies, the pretence--for
it is nothing else, and can be nothing else, than a pretence--of a
knowledge of comparative anatomy as part of their medical curriculum.
Make it part of their Arts teaching if you like, make it part of their
general education if you like, make it part of their qualification for
the scientific degree by all means--that is its proper place; but to
require that gentlemen whose whole faculties should be bent upon
the acquirement of a real knowledge of human physiology should
worry themselves with getting up hearsay about the alternation of
generations in the Salpae is really monstrous. I cannot characterize
it in any other way. And having sacrificed my own pursuit, I am sure I
may sacrifice other people's; and I make this remark with all the
more willingness because I discovered, on reading the name-of your
Professors just now, that the Professor of Materia Medica is not
present. I must confess, if I had my way I should abolish Materia
Medica[1] altogether. I recollect, when I was first under examination
at the University of London, Dr. Pereira was the examiner, and you
know that "Pereira's Materia Medica" was a book _de omnibus rebus_. I
recollect my struggles with that book late at night and early in the
morning (I worked very hard in those days), and I do believe that I
got that book into my head somehow or other, but then I will undertake
to say that I forgot it all a week afterwards. Not one trace of a
knowledge of drugs has remained in my memory from that time to this;
and really, as a matter of common sense, I cannot understand the
arguments for obliging a medical man to know all about drugs and
where they come from. Why not make him belong to the Iron and Steel
Institute, and learn something about cutlery, because he uses knives?
[Footnote 1: It will, I hope, be understood that I do not include
Therapeutics under this head.]
But do not suppose that, after all these deductions, there would not
be ample room for your activity. Let us count up what we have left. I
suppose all the time for medical education that can be hoped for is,
at the outside, about four years. Well, what have you to master in
those four years upon my supposition? Physics applied to physiology;
chemistry applied to physiology; physiology; anatomy; surgery;
medicine (including therapeutics); obstetrics; hygiene; and medical
jurisprudence--nine subjects for four years! And when you consider
what those subjects are, and that the acquisition of anything beyond
the rudiments of any one of them may tax the energies of a lifetime,
I think that even those energies which you young gentlemen have
been displaying for the last hour or two might be taxed to keep you
thoroughly up to what is wanted for your medical career.
I entertain a very strong conviction that any one who adds to medical
education one iota or tittle beyond what is absolutely necessary, is
guilty of a very grave offence. Gentlemen, it will depend upon the
knowledge that you happen to possess,--upon your means of applying it
within your own field of action,--whether the bills of mortality of
your district are increased or diminished; and that, gentlemen, is a
very serious consideration indeed. And, under those circumstances, the
subjects with which you have to deal being so difficult, their extent
so enormous, and the time at your disposal so limited, I could not
feel my conscience easy if I did not, on such an occasion as this,
raise a protest against employing your energies upon the acquisition
of any knowledge which may not be absolutely needed in your future
career.
IV.
YEAST.
IT has been known, from time immemorial, that the sweet liquids which
may be obtained by expressing the juices of the fruits and stems
of various plants, or by steeping malted barley in hot water, or
by mixing honey with water--are liable to undergo a series of very
singular changes, if freely exposed to the air and left to themselves,
in warm weather. However clear and pellucid the liquid may have been
when first prepared, however carefully it may have been freed, by
straining and filtration, from even the finest visible impurities, it
will not remain clear. After a time it will become cloudy and turbid;
little bubbles will be seen rising to the surface, and their abundance
will increase until the liquid hisses as if it were simmering on
the fire. By degrees, some of the solid particles which produce the
turbidity of the liquid collect at its surface into a scum, which
is blown up by the emerging air-bubbles into a thick, foamy froth.
Another moiety sinks to the bottom, and accumulates as a muddy
sediment, or "lees."
When this action has continued, with more or less violence, for
a certain time, it gradually moderates. The evolution of bubbles
slackens, and finally comes to an end; scum and lees alike settle at
the bottom, and the fluid is once more clear and transparent. But
it has acquired properties of which no trace existed in the original
liquid. Instead of being a mere sweet fluid, mainly composed of sugar
and water, the sugar has more or less completely disappeared, and it
has acquired that peculiar smell and taste which we call "spirituous."
Instead of being devoid of any obvious effect upon the animal economy,
it has become possessed of a very wonderful influence on the nervous
system; so that in small doses it exhilarates, while in larger it
stupefies, and may even destroy life.
Moreover, if the original fluid is put into a still, and heated for a
while, the first and last product of its distillation is simple water;
while, when the altered fluid is subjected to the same process, the
matter which is first condensed in the receiver is found to be a
clear, volatile substance, which is lighter than water, has a pungent
taste and smell, possesses the intoxicating powers of the fluid in
an eminent degree, and takes fire the moment it is brought in contact
with a flame. The alchemists called this volatile liquid, which
they obtained from wine, "spirits of wine," just as they called
hydrochloric acid "spirits of salt," and as we, to this day, call
refined turpentine "spirits of turpentine." As the "spiritus," or
breath, of a man was thought to be the most refined and subtle part
of him, the intelligent essence of man was also conceived as a sort
of breath, or spirit; and, by analogy, the most refined essence of
anything was called its "spirit." And thus it has come about that we
use the same word for the soul of man and for a glass of gin.
At the present day, however, we even more commonly use another name
for this peculiar liquid--namely, "alcohol," and its origin is not
less singular. The Dutch physician, Van Helmont, lived in the latter
part of the sixteenth and the beginning of the seventeenth century--in
the transition period between alchemy and chemistry--and was rather
more alchemist than chemist. Appended to his "Opera Omnia," published
in 1707, there is a very needful "Clavis ad obscuriorum sensum
referandum," in which the following passage occurs:--
"ALCOHOL.--Chymicis est liquor aut pulvis summe subtilisatus,
vocabulo Orientalibus quoque, cum primis Habessinis,
familiari, quibus _cohol_ speciatim pulverem impalpabilem ex
antimonio pro oculis tin-gendis denotat ... Hodie autem, ob
analogiam, quivis pulvis teuerior, ut pulvis oculorum cancri
summe subtilisatus _alcohol_ audit, hand aliter ac spiritus
rectificatissimi _alcolisati_ dicuntur."
Similarly, Robert Boyle speaks of a fine powder as "alcohol;" and,
so late as the middle of the last century, the English lexicographer,
Nathan Bailey, defines "alcohol" as "the pure substance of anything
separated from the more gross, a very fine and impalpable powder, or a
very pure, well-rectified spirit." But, by the time of the publication
of Lavoisier's "Traite Elementaire de Chimie," in 1789, the term
"alcohol," "alkohol," or "alkool" (for it is spelt in all three ways),
which Van Helmont had applied primarily to a fine powder, and
only secondarily to spirits of wine, had lost its primary meaning
altogether; and, from the end of the last century until now, it has,
I believe, been used exclusively as the denotation of spirits of wine,
and bodies chemically allied to that substance.
The process which gives rise to alcohol in a saccharine fluid is known
to us as "fermentation;" a term based upon the apparent boiling up or
"effervescence" of the fermenting liquid, and of Latin origin.
Our Teutonic cousins call the same process "gaehren," "gaesen,"
"goeschen," and "gischen;" but, oddly enough, we do not seem to have
retained their verb or their substantive denoting the action itself,
though we do use names identical with, or plainly derived from, theirs
for the scum and lees. These are called, in Low German, "gaescht"
and "gischt;" in Anglo-Saxon, "gest," "gist," and "yst," whence our
"yeast." Again, in Low German and in Anglo-Saxon, there is another
name for yeast, having the form "barm," or "beorm;" and, in the
Midland Counties, "barm" is the name by which yeast is still best
known. In High German, there is a third name for yeast, "hefe," which
is not represented in English, so far as I know.
All these words are said by philologers to be derived from roots
expressive of the intestine motion of a fermenting substance. Thus
"hefe" is derived from "heben," to raise; "barm" from "beren" or
"baeren," to bear up; "yeast," "yst," and "gist," have all to do with
seething and foam, with "yeasty waves," and "gusty" breezes.
The same reference to the swelling up of the fermenting substance is
seen in the Gallo-Latin terms "levure" and "leaven."
It is highly creditable to the ingenuity of our ancestors that the
peculiar property of fermented liquids, in virtue of which they "make
glad the heart of man," seems to have been known in the remotest
periods of which we have any record. All savages take to alcoholic
fluids as if they were to the manner born. Our Vedic forefathers
intoxicated themselves with the juice of the "soma;" Noah, by a not
unnatural reaction against a superfluity of water, appears to have
taken the earliest practicable opportunity of qualifying that which
he was obliged to drink; and the ghosts of the ancient Egyptians were
solaced by pictures of banquets in which the winecup passes round,
graven on the walls of their tombs. A knowledge of the process of
fermentation, therefore, was in all probability possessed by the
prehistoric populations of the globe; and it must have become a matter
of great interest even to primaeval wine-bibbers to study the methods
by which fermented liquids could be surely manufactured. No doubt,
therefore, it was soon discovered that the most certain, as well as
the most expeditious, way of making a sweet juice ferment was to add
to it a little of the scum, or lees, of another fermenting juice.
And it can hardly be questioned that this singular excitation of
fermentation in one fluid, by a sort of infection, or inoculation,
of a little ferment taken from some other fluid, together with the
strange swelling, foaming, and hissing of the fermented substance,
must have always attracted attention from the more thoughtful.
Nevertheless, the commencement of the scientific analysis of the
phenomena dates from a period not earlier than the first half of the
seventeenth century.
At this time, Van Helmont made a first step, by pointing out that the
peculiar hissing and bubbling of a fermented liquid is due, not to the
evolution of common air (which he, as the inventor of the term "gas,"
calls "gas ventosum"), but to that of a peculiar kind of air such
as is occasionally met with in caves, mines, and wells, and which he
calls "gas sylvestre."
But a century elapsed before the nature of this "gas sylvestre," or,
as it was afterwards called, "fixed air," was clearly determined, and
it was found to be identical with that deadly "choke-damp" by which
the lives of those who descend into old wells, or mines, or brewers'
vats, are sometimes suddenly ended; and with the poisonous aeriform
fluid which is produced by the combustion of charcoal, and now goes by
the name of carbonic acid gas.
During the same time it gradually became clear that the presence of
sugar was essential to the production of alcohol and the evolution of
carbonic acid gas, which are the two great and conspicuous products of
fermentation. And finally, in 1787, the Italian chemist, Fabroni, made
the capital discovery that the yeast ferment, the presence of which
is necessary to fermentation, is what he termed a "vegeto-animal"
substance--or is a body which gives off ammoniacal salts when it is
burned, and is, in other ways, similar to the gluten of plants and the
albumen and casein of animals.
These discoveries prepared the way for the illustrious Frenchman,
Lavoisier, who first approached the problem of fermentation with a
complete conception of the nature of the work to be done. The words
in which he expresses this conception, in the treatise on elementary
chemistry to which reference has already been made, mark the year 1789
as the commencement of a revolution of not less moment in the world of
science than that which simultaneously burst over the political world,
and soon engulfed Lavoisier himself in one of its mad eddies.
"We may lay it down as an incontestable axiom that, in all the
operations of art and nature, nothing is created; an equal quantity
of matter exists both before and after the experiment: the quality and
quantity of the elements remain precisely the same, and nothing takes
place beyond changes and modifications in the combinations of these
elements. Upon this principle, the whole art of performing chemical
experiments depends; we must always suppose an exact equality between
the elements of the body examined and those of the products of its
analysis.
"Hence, since from must of grapes we procure alcohol and carbonic
acid, I have an undoubted right to suppose that must consists of
carbonic acid and alcohol. From these premisses we have two modes
of ascertaining what passes during vinous fermentation: either
by determining the nature of, and the elements which compose, the
fermentable substances; or by accurately examining the products
resulting from fermentation; and it is evident that the knowledge
of either of these must lead to accurate conclusions concerning the
nature and composition of the other. From these considerations it
became necessary accurately to determine the constituent elements of
the fermentable substances; and for this purpose I did not make use
of the compound juices of fruits, the rigorous analysis of which
is perhaps impossible, but made choice of sugar, which is easily
analysed, and the nature of which I have already explained. This
substance is a true vegetable oxyd, with two bases, composed of
hydrogen and carbon, brought to the state of an oxyd by means of a
certain proportion of oxygen; and these three elements are combined
in such a way that a very slight force is sufficient to destroy the
equilibrium of their connection."
After giving the details of his analysis of sugar and of the products
of fermentation, Lavoisier continues:--
"The effect of the vinous fermentation upon sugar is thus reduced to
the mere separation of its elements into two portions; one part is
oxygenated at the expense of the other, so as to form carbonic acid;
while the other part, being disoxygenated in favour of the latter, is
converted into the combustible substance called alkohol; therefore,
if it were possible to re-unite alkohol and carbonic acid together, we
ought to form sugar."[1]
[Footnote 1: "Elements of Chemistry." By M. Lavoisier. Translated by
Robert Kerr. Second Edition, 1793 (pp. 186--196).]
Thus Lavoisier thought he had demonstrated that the carbonic acid and
the alcohol which are produced by the process of fermentation, are
equal in weight to the sugar which disappears; but the application of
the more refined methods of modern chemistry to the investigation of
the products of fermentation by Pasteur, in 1860, proved that this is
not exactly true, and that there is a deficit of from 5 to 7 per cent.
of the sugar which is not covered by the alcohol and carbonic acid
evolved. The greater part of this deficit is accounted for by the
discovery of two substances, glycerine and succinic acid, of the
existence of which Lavoisier was unaware, in the fermented liquid.
But about 1-1/2 per cent. still remains to be made good. According to
Pasteur, it has been appropriated by the yeast, but the fact that such
appropriation takes place cannot be said to be actually proved.
However this may be, there can be no doubt that the constituent
elements of fully 98 per cent. of the sugar which has vanished during
fermentation have simply undergone rearrangement; like the soldiers
of a brigade, who at the word of command divide themselves into the
independent regiments to which they belong. The brigade is sugar, the
regiments are carbonic acid, succinic acid, alcohol, and glycerine.
From the time of Fabroni, onwards, it has been admitted that the agent
by which this surprising rearrangement of the particles of the sugar
is effected is the yeast. But the first thoroughly conclusive evidence
of the necessity of yeast for the fermentation of sugar was furnished
by Appert, whose method of preserving perishable articles of food
excited so much attention in France at the beginning of this century.
Gay-Lussac, in his "Memoire sur la Fermentation,"[1] alludes to
Appert's method of preserving beer-wort unfermented for an indefinite
time, by simply boiling the wort and closing the vessel in which the
boiling fluid is contained, in such a way as thoroughly to exclude
air; and he shows that, if a little yeast be introduced into such
wort, after it has cooled, the wort at once begins to ferment, even
though every precaution be taken to exclude air. And this statement
has since received full confirmation from Pasteur.
[Footnote 1: "Annales de Chimie," 1810.]
On the other hand, Schwann, Schroeder and Dusch, and Pasteur, have
amply proved that air may be allowed to have free access to beer-wort,
without exciting fermentation, if only efficient precautions are taken
to prevent the entry of particles of yeast along with the air.
Thus, the truth that the fermentation of a simple solution of sugar in
water depends upon the presence of yeast, rests upon an unassailable
foundation; and the inquiry into the exact nature of the substance
which possesses such a wonderful chemical influence becomes profoundly
interesting.
The first step towards the solution of this problem was made two
centuries ago by the patient and painstaking Dutch naturalist,
Leeuwenhoek, who in the year 1680 wrote thus:--
"Saepissimo examinavi fermentum cerevisiae, semperque hoc ex
globulis per materiam pellucidam fluitantibus, quam cerevisiam
esse censui, constare observavi: vidi etiam evidentissime,
unumquemque hujus fermenti globulum denuo ex sex distinctis
globullis constare, accurate eidem quantitate et formae, cui
globulis sanguinis nostri, respondentibus.
"Verum talis mini de horum origine et formatione conceptus
formabam; globulis nempe ex quibus farina Tritici, Hordei,
Avenae, Fagotritici, se constat aquae calore dissolvi et aquae
commisceri; hac, vero aqua, quam cerevisiam vocare licet,
refrigescente, multos ex minimis particulis in cerevisia
coadunari, et hoc pacto efficere particulam sive globulum,
quae sexta pars est globuli faecis, et iterum sex ex hisce
globulis conjungi."[1]
[Footnote 1: Leeuwenhoek, "Arcana Naturae Detecta." Ed. Nov., 1721.]
Thus Leeuwenhoek discovered that yeast consists of globules floating
in a fluid; but he thought that they were merely the starchy particles
of the grain from which the wort was made, re-arranged. He discovered
the fact that yeast had a definite structure, but not the meaning of
the fact. A century and a half elapsed, and the investigation of
yeast was recommenced almost simultaneously by Cagniard de la Tour in
France, and by Schwann and Kuetzing in Germany. The French observer
was the first to publish his results; and the subject received at his
hands and at those of his colleague, the botanist Turpin, full and
satisfactory investigation.
The main conclusions at which they arrived are these. The globular,
or oval, corpuscles which float so thickly in the yeast as to make it
muddy, though the largest are not more than one two-thousandth of
an inch in diameter, and the smallest may measure less than one
seven-thousandth of an inch, are living organisms. They multiply with
great rapidity, by giving off minute buds, which soon attain the size
of their parent, and then either become detached or remain united,
forming the compound globules of which Leeuwenhoek speaks, though the
constancy of their arrangement in sixes existed only in the worthy
Dutchman's imagination.
It was very soon made out that these yeast organisms, to which Turpin
gave the name of _Torula cerevisiae_, were more nearly allied to the
lower Fungi than to anything else. Indeed Turpin, and subsequently
Berkeley and Hoffmann, believed that they had traced the development
of the _Torula_ into the well-known and very common mould--the
_Penicillium glaucum_. Other observers have not succeeded in verifying
these statements; and my own observations lead me to believe, that
while the connection between _Torula_ and the moulds is a very close
one, it is of a different nature from that which has been supposed. I
have never been able to trace the development of _Torula_ into a true
mould; but it is quite easy to prove that species of true mould,
such as _Penicillium_, when sown in an appropriate nidus, such as
a solution of tartrate of ammonia and yeast-ash, in water, with or
without sugar, give rise to _Torulae_, similar in all respects to _T.
cerevisiae_, except that they are, on the average, smaller. Moreover,
Bail has observed the development of a _Torula_ larger than _T.
cerevisiae_, from a _Mucor_, a mould allied to _Penicillium_.
It follows, therefore, that the _Torulae_, or organisms of yeast,
are veritable plants; and conclusive experiments have proved that the
power which causes the rearrangement of the molecules of the sugar is
intimately connected with the life and growth of the plant. In fact,
whatever arrests the vital activity of the plant also prevents it from
exciting fermentation.
Such being the facts with regard to the nature of yeast, and the
changes which it effects in sugar, how are they to be accounted for?
Before modern chemistry had come into existence, Stahl, stumbling,
with the stride of genius, upon the conception which lies at the
bottom of all modern views of the process, put forward the notion that
the ferment, being in a state of internal motion, communicated
that motion to the sugar, and thus caused its resolution into new
substances. And Lavoisier, as we have seen, adopts substantially the
same view, (But Fabroni, full of the then novel conception of acids
and bases and double decompositions, propounded the hypothesis that
sugar is an oxide with two bases, and the ferment a carbonate with two
bases; that the carbon of the ferment unites with the oxygen of the
sugar, and gives rise to carbonic acid; while the sugar, uniting with
the nitrogen of the ferment, produces a new substance analogous to
opium. This is decomposed by distillation, and gives rise to alcohol.)
Next, in 1803, Thenard propounded a hypothesis which partakes somewhat
of the nature of both Stahl's and Fabroni's views. "I do not believe
with Lavoisier," he says, "that all the carbonic acid formed proceeds
from the sugar. How, in that case, could we conceive the action of the
ferment on it? I think that the first portions of the acid are due
to a combination of the carbon of the ferment with the oxygen of the
sugar, and that it is by carrying off a portion of oxygen from
the last that the ferment causes the fermentation to commence--the
equilibrium between the principles of the sugar being disturbed, they
combine afresh to form carbonic acid and alcohol."
The three views here before us may be familiarly exemplified by
supposing the sugar to be a card-house. According to Stahl, the
ferment is somebody who knocks the table, and shakes the card-house
down; according to Fabroni, the ferment takes out some cards, but puts
others in their places; according to Thenard, the ferment simply takes
a card out of the bottom story, the result of which is that all the
others fall.
As chemistry advanced, facts came to light which put a new face upon
Stahl's hypothesis, and gave it a safer foundation than it previously
possessed. The general nature of these phenomena may be thus
stated:--A body, A, without giving to, or taking from, another
body, B, any material particles, causes B to decompose into other
substances, C, D, E, the sum of the weights of which is equal to the
weight of B, which decomposes.
Thus, bitter almonds contain two substances, amygdalin and synaptase,
which can be extracted, in a separate state, from the bitter almonds.
The amygdalin thus obtained, if dissolved in water, undergoes no
change; but if a little synaptase be added to the solution, the
amygdalin splits up into bitter almond oil, prussic acid, and a kind
of sugar.
A short time after Cagniard de la Tour discovered the yeast plant,
Liebig, struck with the similarity between this and other such
processes and the fermentation of sugar, put forward the hypothesis
that yeast contains a substance which acts upon sugar, as synaptase
acts upon amygdalin. And as the synaptase is certainly neither
organized nor alive, but a mere chemical substance, Liebig treated
Cagniard de la Tour's discovery with no small contempt, and, from
that time to the present, has steadily repudiated the notion that the
decomposition of the sugar is, in any sense, the result of the vital
activity of the _Torula_. But, though the notion that the _Torula_ is
a creature which eats sugar and excretes carbonic acid and alcohol,
which is not unjustly ridiculed in the most surprising paper that
ever made its appearance in a grave scientific journal[1], may be
untenable, the fact that the _Torulae_ are alive, and that yeast does
not excite fermentation unless it contains living _Torulae_, stands
fast. Moreover, of late years, the essential participation of living
organisms in fermentation other than the alcoholic, has been clearly
made out by Pasteur and other chemists.
[Footnote 1: "Das entraethselte Geheimniss der geistigen Gaehrung
(Vorlaeufige briefliche Mittheilung)" is the title of an anonymous
contribution, to Woehler and Liebig's "Annalen der Pharmacie" for
1839, in which a somewhat Rabelaisian imaginary description of the
organization of the "yeast animals" and of the manner in which their
functions are performed, is given with a circumstantiality worthy
of the author of Gulliver's Travels. As a specimen of the writer's
humour, his account of what happens when fermentation comes to an end
may suffice. "Sobald naemlich die Thiere keinen Zucker mehr vorfinden,
so fressen sie sich gegenseitig selbst auf, was durch eine eigene
Manipulation geschicht; alles wird verdaut bis auf die Eier, welche
unveraendert durch den Darmkanal hineingehen; man hat zuletzt wieder
gaehrungsfaehige Hefe, naemlich den Saamen der Thiere, der uebrig
bleibt."]
However, it may be asked, is there any necessary opposition between
the so-called "vital" and the strictly physico-chemical views of
fermentation? It is quite possible that the living _Torula_ may excite
fermentation in sugar, because it constantly produces, as an essential
part of its vital manifestations, some substance which acts upon the
sugar, just as the synaptase acts upon the amygdalin. Or it may
be, that, without the formation of any such special substance,
the physical condition of the living tissue of the yeast plant is
sufficient to effect that small disturbance of the equilibrium of the
particles of the sugar, which Lavoisier thought sufficient to effect
its decomposition.
Platinum in a very fine state of division--known as platinum black, or
_noir de platine_--has the very singular property of causing alcohol
to change into acetic acid with great rapidity. The vinegar plant,
which is closely allied to the yeast plant, has a similar effect upon
dilute alcohol, causing it to absorb the oxygen of the air, and become
converted into vinegar; and Liebig's eminent opponent, Pasteur, who
has done so much for the theory and the practice of vinegar-making,
himself suggests that in this case--
"La cause du phenomene physique qui accompagne la vie de la
plante reside dans un etat physique propre, analogue a celui
du noir de platine. Mais il est essentiel de remarquer que cet
etat physique de la plante est etroitement lie avec la vie de
cette plante."[1]
[Footnote 1: "Etudes sur les Mycodermes," Comptes-Rendus, liv., 1862.]
Now, if the vinegar plant gives rise to the oxidation of alcohol,
on account of its merely physical constitution, it is at any rate
possible that the physical constitution of the yeast plant may exert a
decomposing influence on sugar.
But, without presuming to discuss a question which leads us into the
very arcana of chemistry, the present state of speculation upon the
_modus operandi_ of the yeast plant in producing fermentation is
represented, on the one hand, by the Stahlian doctrine, supported by
Liebig, according to which the atoms of the sugar are shaken into new
combinations, either directly by the _Torulae_, or indirectly, by some
substance formed by them; and, on the other hand, by the Thenardian
doctrine, supported by Pasteur, according to which the yeast plant
assimilates part of the sugar, and, in so doing, disturbs the rest,
and determines its resolution into the products of fermentation.
Perhaps the two views are not so much opposed as they seem at first
sight to be.
But the interest which attaches to the influence of the yeast plants
upon the medium in which they live and grow does not arise solely
from its bearing upon the theory of fermentation. So long ago as 1838,
Turpin compared the _Torulae_ to the ultimate elements of the tissues
of animals and plants--"Les organes elementaires de leurs tissus,
comparables aux petits vegetaux des levures ordinaires, sont aussi les
decompositeurs des substances qui les environnent."
Almost at the same time, and, probably, equally guided by his study of
yeast, Schwann was engaged in those remarkable investigations into
the form and development of the ultimate structural elements of the
tissues of animals, which led him to recognize their fundamental
identity with the ultimate structural elements of vegetable organisms.
The yeast plant is a mere sac, or "cell," containing a semi-fluid
matter, and Schwann's microscopic analysis resolved all living
organisms, in the long run, into an aggregation of such sacs or cells,
variously modified; and tended to show, that all, whatever their
ultimate complication, begin their existence in the condition of such
simple cells.
In his famous "Mikroskopische Untersuchungen," Schwann speaks of
_Torula_ as a "cell;" and, in a remarkable note to the passage in
which he refers to the yeast plant, Schwann says:--
"I have been unable to avoid mentioning fermentation, because
it is the most fully and exactly known operation of cells,
and represents, in the simplest fashion, the process which is
repeated by every cell of the living body."
In other words, Schwann conceives that every cell of the living body
exerts an influence on the matter which surrounds and permeates it,
analogous to that which a _Torula_ exerts on the saccharine solution
by which it is bathed. A wonderfully suggestive thought, opening up
views of the nature of the chemical processes of the living body,
which have hardly yet received all the development of which they are
capable.
Kant defined the special peculiarity of the living body to be that the
parts exist for the sake of the whole and the whole for the sake of
the parts. But when Turpin and Schwann resolved the living body into
an aggregation of quasi-independent cells, each, like a _Torula_,
leading its own life and having its own laws of growth and
development, the aggregation being dominated and kept working towards
a definite end only by a certain harmony among these units, or by the
superaddition of a controlling apparatus, such as a nervous system,
this conception ceased to be tenable. The cell lives for its own sake,
as well as for the sake of the whole organism; and the cells, which
float in the blood, live at its expense, and profoundly modify it, are
almost as much independent organisms as the _Torulae_ which float in
beer-wort.
Schwann burdened his enunciation of the "cell theory" with two false
suppositions; the one, that the structures he called "nucleus" and
"cell-wall" are essential to a cell; the other, that cells are usually
formed independently of other cells; but, in 1839, it was a vast and
clear gain to arrive at the conception, that the vital functions of
all the higher animals and plants are the resultant of the forces
inherent in the innumerable minute cells of which they are composed,
and that each of them is, itself, an equivalent of one of the lowest
and simplest of independent living beings--the _Torula._
From purely morphological investigations, Turpin and Schwann, as we
have seen, arrived at the notion of the fundamental unity of structure
of living beings. And, before long, the researches of chemists
gradually led up to the conception of the fundamental unity of their
composition.
So far back as 1803, Thenard pointed out, in most distinct terms, the
important fact that yeast contains a nitrogenous "animal" substance;
and that such a substance is contained in all ferments. Before him,
Fabroni and Fourcroy speak of the "vegeto-animal" matter of yeast.
In 1844 Mulder endeavoured to demonstrate that a peculiar substance,
which he called "protein," was essentially characteristic of living
matter. In 1846, Payen writes:--
"Enfin, une loi sans exception me semble apparaitre dans les
faits nombreux que j'ai observes et conduire a envisager sous
un nouveau jour la vie vegetale; si je ne m'abuse, tout ce
que dans les tissus vegetaux la vue directe ou amplifiee nous
permet de discerner sous la forme de cellules et de vaisseaux,
ne represente autre chose que les enveloppes protectrices,
les reservoirs et les conduits, a l'aide desquels les corps
animes qui les secretent et les faconnent, se logent, puisent
et charriant leurs aliments, deposent et isolent les matieres
excretees."
And again:--
"A fin de completer aujourd'hui l'enonce du fait general, je
rappellerai que les corps, doue des fonctions accomplies
dans les tissus des plantes, sont formes des elements qui
constituent, en proportion peu variable, les organismes
animaux; qu'ainsi l'on est conduit a reconnaitre une immense
unite de composition elementaire dans tous les corps vivants
de la nature."[1]
[Footnote 1: "Mem. sur les Developpements des Vegetaux," &c.--"Mem.
Presentees." ix. 1846.]
In the year (1846) in which these remarkable passages were published,
the eminent German botanist, Von Mohl, invented the word "protoplasm,"
as a name for one portion of those nitrogenous contents of the cells
of living plants, the close chemical resemblance of which to the
essential constituents of living animals is so strongly indicated by
Payen. And through the twenty-five years that have passed, since the
matter of life was first called protoplasm, a host of investigators,
among whom Cohn, Max Schulze, and Kuehne must be named as leaders, have
accumulated evidence, morphological, physiological, and chemical, in
favour of that "immense unite de composition elementaire dans tous les
corps vivants de la nature," into which Payen had, so early, a clear
insight.
As far back as 1850, Cohn wrote, apparently without any knowledge of
what Payen had said before him:--
"The protoplasm of the botanist, and the contractile substance
and sarcode of the zoologist, must be, if not identical, yet
in a high degree analogous substances. Hence, from this point
of view, the difference between animals and plants consists
in this; that, in the latter, the contractile substance, as
a primordial utricle, is enclosed within an inert cellulose
membrane, which permits it only to exhibit an internal motion,
expressed by the phenomena of rotation and circulation, while,
in the former, it is not so enclosed. The protoplasm in the
form of the primordial utricle is, as it were, the animal
element in the plant, but which is imprisoned, and only
becomes free in the animal; _or_, to strip off the metaphor
which obscures simple thought, the energy of organic vitality
which is manifested in movement is especially exhibited by a
nitrogenous contractile substance, which in plants is limited
and fettered by an inert membrane, in animals not so."[1]
[Footnote 1: Cohn, "Ueber Protococcus pluvialis," in the "Nova Acta"
for 1850.]
In 1868, thinking that an untechnical statement of the views current
among the leaders of biological science might be interesting to the
general public, I gave a lecture embodying them in Edinburgh. Those
who have not made the mistake of attempting to approach biology,
either by the high _a priori_ road of mere philosophical speculation,
or by the mere low _a posteriori_ lane offered by the tube of a
microscope, but have taken the trouble to become acquainted with
well-ascertained facts and with their history, will not need to be
told that in what I had to say "as regards protoplasm" in my lecture
"On the Physical Basis of Life," there was nothing new; and, as I
hope, nothing that the present state of knowledge does not justify us
in believing to be true. Under these circumstances, my surprise may be
imagined, when I found, that the mere statement of facts and of views,
long familiar to me as part of the common scientific property of
continental workers, raised a sort of storm in this country, not only
by exciting the wrath of unscientific persons whose pet prejudices
they seemed to touch, but by giving rise to quite superfluous
explosions on the part of some who should have been better informed.
Dr. Stirling, for example, made my essay the subject of a special
critical lecture[1], which I have read with much interest, though, I
confess, the meaning of much of it remains as dark to me as does the
"Secret of Hegel" after Dr. Stirling's elaborate revelation of it.
Dr. Stirling's method of dealing with the subject is peculiar.
"Protoplasm" is a question of history, so far as it is a name; of
fact, so far as it is a thing. Dr. Stirling has not taken the trouble
to refer to the original authorities for his history, which is
consequently a travesty; and still less has he concerned himself with
looking at the facts, but contents himself with taking them also at
secondhand. A most amusing example of this fashion of dealing with
scientific statements is furnished by Dr. Stirling's remarks upon my
account of the protoplasm of the nettle hair. That account was drawn
up from careful and often-repeated observation of the facts. Dr.
Stirling thinks he is offering a valid criticism, when he says that my
valued friend Professor Stricker gives a somewhat different statement
about protoplasm. But why in the world did not this distinguished
Hegelian look at a nettle hair for himself, before venturing to
speak about the matter at all? Why trouble himself about what either
Stricker or I say, when any tyro can see the facts for himself, if he
is provided with those not rare articles, a nettle and a microscope?
But I suppose this would have been "_Aufklaerung_"--a recurrence to the
base common-sense philosophy of the eighteenth century, which liked
to see before it believed, and to understand before it criticised. Dr.
Stirling winds up his paper with the following paragraph:--
[Footnote 1: Subsequently published under the title of "As regards
Protoplasm."]
"In short, the whole position of Mr. Huxley, (1) that all
organisms consist alike of the same life-matter, (2) which
life-matter is, for its part, due only to chemistry, must be
pronounced untenable--nor less untenable (3) the materialism
he would found on it."
The paragraph contains three distinct assertions concerning my views,
and just the same number of utter misrepresentations of them. That
which I have numbered (1) turns on the ambiguity of the word "same,"
for a discussion of which I would refer Dr. Stirling to a great hero
of "_Aufklaerung_", Archbishop Whately; statement number (2) is, in my
judgment, absurd, and certainly I have never said anything resembling
it; while, as to number (3), one great object of my essay was to show
that what is called "materialism," has no sound philosophical basis!
As we have seen, the study of yeast has led investigators face to face
with problems of immense interest in pure chemistry, and in animal and
vegetable morphology. Its physiology is not less rich in subjects for
inquiry. Take, for example, the singular fact that yeast will increase
indefinitely when grown in the dark, in water containing only tartrate
of ammonia, a small percentage of mineral salts, and sugar. Out of
these materials the _Torulae_ will manufacture nitrogenous protoplasm,
cellulose, and fatty matters, in any quantity, although they are
wholly deprived of those rays of the sun, the influence of which is
essential to the growth of ordinary plants. There has been a great
deal of speculation lately, as to how the living organisms buried
beneath two or three thousand fathoms of water, and therefore in all
probability almost deprived of light, live.
If any of them possess the same powers as yeast (and the same capacity
for living without light is exhibited by some other fungi) there would
seem to be no difficulty about the matter.
Of the pathological bearings of the study of yeast, and other such
organisms, I have spoken elsewhere. It is certain that, in
some animals, devastating epidemics are caused by fungi of low
order--similar to those of which _Torula_ is a sort of offshoot. It is
certain that such diseases are propagated by contagion and infection,
in just the same way as ordinary contagious and infectious diseases
are propagated. Of course, it does not follow from this, that all
contagious and infectious diseases are caused by organisms of as
definite and independent a character as the _Torula_; but, I think,
it does follow that it is prudent and wise to satisfy oneself in each
particular case, that the "germ theory" cannot and will not explain
the facts, before having recourse to hypotheses which have no equal
support from analogy.
V.
ON THE FORMATION OF COAL.
The lumps of coal in a coal-scuttle very often have a roughly cubical
form. If one of them be picked out and examined with a little care, it
will be found that its six sides are not exactly alike. Two opposite
sides are comparatively smooth and shining, while the other four are
much rougher, and are marked by lines which run parallel with the
smooth sides. The coal readily splits along these lines, and the split
surfaces thus formed are parallel with the smooth faces. In other
words, there is a sort of rough and incomplete stratification in the
lump of coal, as if it were a book, the leaves of which had stuck
together very closely.
Sometimes the faces along which the coal splits are not smooth, but
exhibit a thin layer of dull, charred-looking substance, which is
known as "mineral charcoal."
Occasionally one of the faces of a lump of coal will present
impressions, which are obviously those of the stem, or leaves, of a
plant; but though hard mineral masses of pyrites, and even fine mud,
may occur here and there, neither sand nor pebbles are met with.
When the coal burns, the chief ultimate products of its combustion
are carbonic acid, water, and ammoniacal products, which escape up the
chimney; and a greater or less amount of residual earthy salts, which
take the form of ash. These products are, to a great extent, such as
would result from the burning of so much wood.
These properties of coal may be made out without any very refined
appliances, but the microscope reveals something more. Black and
opaque as ordinary coal is, slices of it become transparent if they
are cemented in Canada balsam, and rubbed down very thin, in the
ordinary way of making thin sections of non-transparent bodies. But
as the thin slices, made in this way, are very apt to crack and break
into fragments, it is better to employ marine glue as the cementing
material. By the use of this substance, slices of considerable size
and of extreme thinness and transparency may be obtained.[1]
[Footnote 1: My assistant in the Museum of Practical Geology, Mr.
Newton, invented this excellent method of obtaining thin slices of
coal.]
Now let us suppose two such slices to be prepared from our lump of
coal--one parallel with the bedding, the other perpendicular to it;
and let us call the one the horizontal, and the other the vertical,
section. The horizontal section will present more or less rounded
yellow patches and streaks, scattered irregularly through the dark
brown, or blackish, ground substance; while the vertical section will
exhibit more elongated bars and granules of the same yellow materials,
disposed in lines which correspond, roughly, with the general
direction of the bedding of the coal.
This is the microscopic structure of an ordinary piece of coal. But if
a great series of coals, from different localities and seams, or even
from different parts of the same seam, be examined, this structure
will be found to vary in two directions. In the anthracitic, or
stone-coals, which burn like coke, the yellow matter diminishes, and
the ground substance becomes more predominant, and blacker, and more
opaque, until it becomes impossible to grind a section thin enough to
be translucent; while, on the other hand, in such as the "Better-Bed"
coal of the neighbourhood of Bradford, which burns with much flame,
the coal is of a far lighter colour, and transparent sections are very
easily obtained. In the browner parts of this coal, sharp eyes will
readily detect multitudes of curious little coin-shaped bodies, of a
yellowish brown colour, embedded in the dark brown ground substance.
On the average, these little brown bodies may have a diameter of about
one-twentieth of an inch. They lie with their flat surfaces nearly
parallel with the two smooth faces of the block in which they are
contained; and, on one side of each, there may be discerned a figure,
consisting of three straight linear marks, which radiate from the
centre of the disk, but do not quite reach its circumference. In the
horizontal section these disks are often converted into more or less
complete rings; while in the vertical sections they appear like thick
hoops, the sides of which have been pressed together. The disks are,
therefore, flattened bags; and favourable sections show that the
three-rayed marking is the expression of three clefts, which penetrate
one wall of the bag.
The sides of the bags are sometimes closely approximated; but, when
the bags are less flattened, their cavities are, usually, filled with
numerous, irregularly rounded, hollow bodies, having the same kind of
wall as the large ones, but not more than one seven-hundredth of an
inch in diameter.
In favourable specimens, again, almost the whole ground substance
appears to be made up of similar bodies--more or less carbonized
or blackened--and, in these, there can be no doubt that, with the
exception of patches of mineral charcoal, here and there, the whole
mass of the coal is made up of an accumulation of the larger and of
the smaller sacs.
But, in one and the same slice, every transition can be observed from
this structure to that which has been described as characteristic of
ordinary coal. The latter appears to rise out of the former, by the
breaking-up and increasing carbonization of the larger and the smaller
sacs. And, in the anthracitic coals, this process appears to have gone
to such a length, as to destroy the original structure altogether, and
to replace it by a completely carbonized substance.
Thus coal may be said, speaking broadly, to be composed of two
constituents: firstly, mineral charcoal; and, secondly, coal proper.
The nature of the mineral charcoal has long since been determined. Its
structure shows it to consist of the remains of the stems and leaves
of plants, reduced to little more than their carbon. Again, some of
the coal is made up of the crushed and flattened bark, or outer coat,
of the stems of plants, the inner wood of which has completely decayed
away. But what I may term the "saccular matter" of the coal, which,
either in its primary or in its degraded form, constitutes by far the
greater part of all the bituminous coals I have examined, is certainly
not mineral charcoal; nor is its structure that of any stem or leaf.
Hence its real nature is, at first, by no means apparent, and has been
the subject of much discussion.
The first person who threw any light upon the problem, as far as I
have been able to discover, was the well-known geologist, Professor
Morris. It is now thirty-four years since he carefully described and
figured the coin-shaped bodies, or larger sacs, as I have called
them, in a note appended to the famous paper "On the Coal-brookdale
Coal-Field," published at that time, by the present President of
the Geological Society, Mr. Prestwich. With much sagacity, Professor
Morris divined the real nature of these bodies, and boldly
affirmed them to be the spore-cases of a plant allied to the living
club-mosses.
But discovery sometimes makes a long halt; and it is only a few
years since Mr. Carruthers determined the plant (or rather one of the
plants) which produces these spore-cases, by finding the discoidal
sacs still adherent to the leaves of the fossilized cone which
produced them. He gave the name of _Flemingites gracilis_ to the plant
of which the cones form a part. The branches and stem of this plant
are not yet certainly known, but there is no sort of doubt that it was
closely allied to the _Lepidodendron_, the remains of which abound in
the coal formation. The _Lepidodendra_ were shrubs and trees which put
one more in mind of an _Araucaria_ than of any other familiar plant;
and the ends of the fruiting branches were terminated by cones, or
catkins, somewhat like the bodies so named in a fir, or a willow.
These conical fruits, however, did not produce seeds; but the leaves
of which they were composed bore upon their surfaces sacs full of
spores or sporangia, such as those one sees on the under surface of a
bracken leaf. Now, it is these sporangia of the Lepidodendroid plant
_Flemingites_ which were identified by Mr. Carruthers with the free
sporangia described by Professor Morris, which are the same as the
large sacs of which I have spoken. And, more than this, there is
no doubt that the small sacs are the spores, which were originally
contained in the sporangia.
The living club-mosses are, for the most part, insignificant and
creeping herbs, which, superficially, very closely resemble true
mosses, and none of them reach more than two or three feet in height.
But, in their essential structure, they very closely resemble the
earliest Lepidodendroid trees of the coal: their stems and leaves are
similar; so are their cones; and no less like are the sporangia and
spores; while even in their size, the spores of the _Lepidodendron_
and those of the existing _Lycopodium_, or club-moss, very closely
approach one another.
Thus, the singular conclusion is forced upon us, that the greater and
the smaller sacs of the "Better-Bed" and other coals, in which the
primitive structure is well preserved, are simply the sporangia and
spores of certain plants, many of which were closely allied to the
existing club-mosses. And if, as I believe, it can be demonstrated
that ordinary coal is nothing but "saccular" coal which has undergone
a certain amount of that alteration which, if continued, would convert
it into anthracite; then, the conclusion is obvious, that the great
mass of the coal we burn is the result of the accumulation of the
spores and spore-cases of plants, other parts of which have furnished
the carbonized stems and the mineral charcoal, or have left their
impressions on the surfaces of the layer.
Of the multitudinous speculations which, at various times, have been
entertained respecting the origin and mode of formation of coal,
several appear to be negatived, and put out of court, by the
structural facts the significance of which I have endeavoured to
explain. These facts, for example, do not permit us to suppose that
coal is an accumulation of peaty matter, as some have held.
Again, the late Professor Quekett was one of the first observers
who gave a correct description of what I have termed the "saccular"
structure of coal; and, rightly perceiving that this structure was
something quite different from that of any known plant, he imagined
that it proceeded from some extinct vegetable organism which was
peculiarly abundant amongst the coal-forming plants. But this
explanation is at once shown to be untenable when the smaller and the
larger sacs are proved to be spores or sporangia.
Some, once more, have imagined that coal was of submarine origin; and
though the notion is amply and easily refuted by other considerations,
it may be worth while to remark, that it is impossible to comprehend
how a mass of light and resinous spores should have reached the bottom
of the sea, or should have stopped in that position if they had got
there.
At the same time, it is proper to remark that I do not presume to
suggest that all coal must needs have the same structure; or that
there may not be coals in which the proportions of wood and spores, or
spore-cases, are very different from those which I have examined. All
I repeat is, that none of the coals which have come under my notice
have enabled me to observe such a difference. But, according to
Principal Dawson, who has so sedulously examined the fossil remains of
plants in North America, it is otherwise with the vast accumulations
of coal in that country.
"The true coal," says Dr. Dawson, "consists principally of
the flattened bark of Sigillarioid and other trees, intermixed
with leaves of Ferns and _Cordaites_, and other herbaceous
_debris_, and with fragments of decayed wood, constituting
'mineral charcoal,' all these materials having manifestly
alike grown and accumulated where we find them."[1]
[Footnote 1: "Acadian Geology," 2nd edition, p. 138.]
When I had the pleasure of seeing Principal Dawson in London last
summer, I showed him my sections of coal, and begged him to re-examine
some of the American coals on his return to Canada, with an eye to the
presence of spores and sporangia, such as I was able to show him in
our English and Scotch coals. He has been good enough to do so; and in
a letter dated September 26th, 1870, he informs me that--
"Indications of spore-cases are rare, except in certain coarse
shaly coals and portions of coals, and in the roofs of the
seams. The most marked case I have yet met with is the shaly
coal referred to as containing _Sporangites_ in my paper
on the conditions of accumulation of coal (_Journal of the
Geological Society_, vol. xxii. pp. 115, 139, and 165). The
purer coals certainly consist principally of cubical tissues
with some true woody matter, and the spore-cases, &c.,
are chiefly in the coarse and shaly layers. This is my old
doctrine in my two papers in the _Journal of the Geological
Society_, and I see nothing to modify it. Your observations,
however, make it probable that the frequent _clear spots_ in
the cannels are spore-cases."
Dr. Dawson's results are the more remarkable, as the numerous
specimens of British coal, from various localities, which I have
examined, tell one tale as to the predominance of the spore and
sporangium element in their composition; and as it is exactly in the
finest and purest coals, such as the "Better-Bed" coal of Lowmoor,
that the spores and sporangia obviously constitute almost the entire
mass of the deposit.
Coal, such as that which has been described, is always found in
sheets, or "seams," varying from a fraction of an inch to many feet
in thickness, enclosed in the substance of the earth at very various
depths, between beds of rock of different kinds. As a rule, every seam
of coal rests upon a thicker, or thinner, bed of clay, which is known
as "under-clay." These alternations of beds of coal, clay, and rock
may be repeated many times, and are known as the "coal-measures;"
and in some regions, as in South Wales and in Nova Scotia, the
coal-measures attain a thickness of twelve or fourteen thousand
feet, and enclose eighty or a hundred seams of coal, each with its
under-clay, and separated from those above and below by beds of
sandstone and shale.
The position of the beds which constitute the coal-measures is
infinitely diverse. Sometimes they are tilted up vertically, sometimes
they are horizontal, sometimes curved into great basins; sometimes
they come to the surface, sometimes they are covered up by thousands
of feet of rock. But, whatever their present position, there is
abundant and conclusive evidence that every under-clay was once a
surface soil. Not only do carbonized root-fibres frequently abound in
these under-clays; but the stools of trees, the trunks of which are
broken off and confounded with the bed of coal, have been repeatedly
found passing into radiating roots, still embedded in the under-clay.
On many parts of the coast of England, what are commonly known as
"submarine forests" are to be seen at low water. They consist, for the
most part, of short stools of oak, beech, and fir trees, still fixed
by their long roots in the bed of blue clay in which they originally
grew. If one of these submarine forest beds should be gradually
depressed and covered up by new deposits, it would present just the
same characters as an under-clay of the coal, if the _Sigillaria_ and
_Lepidodendron_ of the ancient world were substituted for the oak, or
the beech, of our own times.
In a tropical forest, at the present day, the trunks of fallen trees,
and the stools of such trees as may have been broken by the violence
of storms, remain entire for but a short time. Contrary to what might
be expected, the dense wood of the tree decays, and suffers from the
ravages of insects, more swiftly than the bark. And the traveller,
setting his foot on a prostrate trunk, finds that it is a mere shell,
which breaks under his weight, and lands his foot amidst the insects,
or the reptiles, which have sought food or refuge within.
The trees of the coal forests present parallel conditions. When the
fallen trunks which have entered into the composition of the bed of
coal are identifiable, they are mere double shells of bark, flattened
together in consequence of the destruction of the woody core; and Sir
Charles Lyell and Principal Dawson discovered, in the hollow stools
of coal trees of Nova Scotia, the remains of snails, millipedes,
and salamander-like creatures, embedded in a deposit of a different
character from that which surrounded the exterior of the trees. Thus,
in endeavouring to comprehend the formation of a seam of coal, we must
try to picture to ourselves a thick forest, formed for the most part
of trees like gigantic club-mosses, mares-tails, and tree ferns, with
here and there some that had more resemblance to our existing yews and
fir-trees. We must suppose that, as the seasons rolled by, the plants
grew and developed their spores and seeds; that they shed these in
enormous quantities, which accumulated on the ground beneath; and
that, every now and then, they added a dead frond or leaf; or, at
longer intervals, a rotten branch, or a dead trunk, to the mass.
A certain proportion of the spores and seeds no doubt fulfilled their
obvious function, and, carried by the wind to unoccupied regions,
extended the limits of the forest; many might be washed away by rain
into streams, and be lost; but a large portion must have remained, to
accumulate like beech-mast, or acorns, beneath the trees of a modern
forest.
But, in this case, it may be asked, why does not our English coal
consist of stems and leaves to a much greater extent than it does?
What is the reason of the predominance of the spores and spore-cases
in it?
A ready answer to this question is afforded by the study of a living
full-grown club-moss. Shake it upon a piece of paper, and it emits a
cloud of fine dust, which falls over the paper, and is the well-known
Lycopodium powder. Now this powder used to be, and I believe still
is, employed for two objects, which seem at first sight to have no
particular connection with one another. It is, or was, employed in
making lightning, and in making pills. The coats of the spores contain
so much resinous matter, that a pinch of Lycopodium powder, thrown
through the flame of a candle, burns with an instantaneous flash,
which has long done duty for lightning on the stage. And the same
character makes it a capital coating for pills; for the resinous
powder prevents the drug from being wetted by the saliva, and thus
bars the nauseous flavour from the sensitive papillae of the tongue.
But this resinous matter, which lies in the walls of the spores and
sporangia, is a substance not easily altered by air and water,
and hence tends to preserve these bodies, just as the bituminized
cerecloth preserves an Egyptian mummy; while, on the other hand, the
merely woody stem and leaves tend to rot, as fast as the wood of the
mummy's coffin has rotted. Thus the mixed heap of spores, leaves,
and stems in the coal-forest would be persistently searched by the
long-continued action of air and rain; the leaves and stems would
gradually be reduced to little but their carbon, or, in other words,
to the condition of mineral charcoal in which we find them; while the
spores and sporangia remained as a comparatively unaltered and compact
residuum.
There is, indeed, tolerably clear evidence that the coal must, under
some circumstances, have been converted into a substance hard enough
to be rolled into pebbles, while it yet lay at the surface of the
earth; for in some seams of coal, the courses of rivulets, which must
have been living water, while the stratum in which their remains are
found was still at the surface, have been observed to contain rolled
pebbles of the very coal through which the stream has cut its way.
The structural facts are such as to leave no alternative but to adopt
the view of the origin of such coal as I have described, which has
just been stated; but, happily, the process is not without analogy at
the present day. I possess a specimen of what is called "white coal"
from Australia. It is an inflammable material, burning with a bright
flame, and having much the consistence and appearance of oat-cake,
which, I am informed, covers a considerable area. It consists, almost
entirely, of a compacted mass of spores and spore-cases. But the fine
particles of blown sand which are scattered through it, show that it
must have accumulated, subaerially, upon the surface of a soil covered
by a forest of cryptogamous plants, probably tree-ferns.
As regards this important point of the subaerial region of coal, I am
glad to find myself in entire accordance with Principal Dawson,
who bases his conclusions upon other, but no less forcible,
considerations. In a passage, which is the continuation of that
already cited, he writes:--
"(3) The microscopical structure and chemical composition of
the beds of cannel coal and earthy bitumen, and of the more
highly bituminous and carbonaeceous shale, show them to have
been of the nature of the fine vegetable mud which accumulates
in the ponds and shallow lakes of modern swamps. When such
fine vegetable sediment is mixed, as is often the case, with
clay, it becomes similar to the bituminous limestone and
calcareo-bituminous shales of the coal-measures. (4) A few of
the under-clays, which support beds of coal, are of the nature
of the vegetable mud above referred to; but the greater part
are argillo-arenaceous in composition, with little vegetable
matter, and bleached by the drainage from them of water
containing the products of vegetable decay. They are, in
short, loamy or clay soils, and must have been sufficiently
above water to admit of drainage. The absence of sulphurets,
and the occurrence of carbonate of iron in connection with
them, prove that, when they existed as soils, rain-water, and
not sea-water, percolated them. (5) The coal and the fossil
forests present many evidences of subaerial conditions. Most
of the erect and prostrate trees had become hollow shells of
bark before they were finally embedded, and their wood had
broken into cubical pieces of mineral charcoal. Land-snails
and galley-worms _Xylobius_ crept into them, and they became
dens, or traps, for reptiles. Large quantities of mineral
charcoal occur on the surface of all the large beds of
coal. None of these appearances could have been produced by
subaqueous action. (6) Though the roots of the _Sigillaria_
bear more resemblance to the rhizomes of certain aquatic
plants; yet, structurally, they are absolutely identical with
the roots of Cycads, which the stems also resemble. Further,
the _Sigillariae_ grew on the same soils which supported
Conifers, _Lepidodendra, Cordaites_, and Ferns--plants which
could not have grown in water. Again, with the exception
perhaps of some _Pinnulariae_ and _Asterophyllites_, there
is a remarkable absence from the coal measures of any form of
properly aquatic vegetation. (7) The occurrence of marine, or
brackish-water animals, in the roofs of coal-beds, or even
in the coal itself, affords no evidence of subaqueous
accumulation, since the same thing occurs in the case of
modern submarine forests. For these and other reasons, some of
which are more fully stated in the papers already referred
to, while I admit that the areas of coal accumulation were
frequently submerged, I must maintain that the true coal is a
subaerial accumulation by vegetable growth on soils, wet and
swampy it is true, but not submerged."
I am almost disposed to doubt whether it is necessary to make the
concession of "wet and swampy;" otherwise, there is nothing that I
know of to be said against this excellent conspectus of the reasons
for believing in the subaerial origin of coal.
But the coal accumulated upon the area covered by one of the great
forests of the carboniferous epoch would, in course of time, have
been wasted away by the small, but constant, wear and tear of rain and
streams, had the land which supported it remained at the same level,
or been gradually raised to a greater elevation. And, no doubt, as
much coal as now exists has been destroyed, after its formation, in
this way. What are now known as coal districts owe their importance to
the fact that they were areas of slow depression, during a greater or
less portion of the carboniferous epoch; and that, in virtue of this
circumstance, Mother Earth was enabled to cover up her vegetable
treasures, and preserve them from destruction.
Wherever a coal-field now exists, there must formerly have been free
access for a great river, or for a shallow sea, bearing sediment in
the shape of sand and mud. When the coal-forest area became slowly
depressed, the waters must have spread over it, and have deposited
their burden upon the surface of the bed of coal, in the form of
layers, which are now converted into shale, or sandstone. Then
followed a period of rest, in which the superincumbent shallow waters
became completely filled up, and finally replaced, by fine mud, which
settled down into a new under-clay, and furnished the soil for a fresh
forest growth. This flourished, and heaped up its spores and wood into
coal, until the stage of slow depression recommenced. And, in some
localities, as I have mentioned, the process was repeated until the
first of the alternating beds had sunk to near three miles below its
original level at the surface of the earth.
In reflecting on the statement, thus briefly made, of the main facts
connected with the origin of the coal formed during the carboniferous
epoch, two or three considerations suggest themselves.
In the first place, the great phantom of geological time rises before
the student of this, as of all other, fragments of the history of our
earth--springing irrepressibly out of the facts, like the Djin from
the jar which the fisherman so incautiously opened; and like the Djin
again, being vaporous, shifting, and indefinable, but unmistakably
gigantic. However modest the bases of one's calculation may be,
the minimum of time assignable to the coal period remains something
stupendous.
Principal Dawson is the last person likely to be guilty of
exaggeration in this matter, and it will be well to consider what he
has to say about it:--
"The rate of accumulation of coal was very slow. The climate
of the period, in the northern temperate zone, was of such
a character that the true conifers show rings of growth, not
larger, nor much less distinct, than those of many of their
modern congeners. The _Sigillariae_ and _Calamites_ were not,
as often supposed, composed wholly, or even principally, of
lax and soft tissues, or necessarily short-lived. The former
had, it is true, a very thick inner bark; but their dense
woody axis, their thick and nearly imperishable outer bark,
and their scanty and rigid foliage, would indicate no very
rapid growth or decay. In the case of the _Sigillariae_, the
variations in the leaf-scars in different parts of the trunk,
the intercalation of new ridges at the surface representing
that of new woody wedges in the axis, the transverse marks
left by the stages of upward growth, all indicate that several
years must have been required for the growth of stems of
moderate size. The enormous roots of these trees, and the
condition of the coal-swamps, must have exempted them from the
danger of being overthrown by violence. They probably fell in
successive generations from natural decay; and making every
allowance for other materials, we may safely assert that every
foot of thickness of pure bituminous coal implies the
quiet growth and fall of at least fifty generations of
_Sigillariae_, and therefore an undisturbed condition of
forest growth enduring through many centuries. Further, there
is evidence that an immense amount of loose parenchymatous
tissue, and even of wood, perished by decay, and we do not
know to what extent even the most durable tissues may have
disappeared in this way; so that, in many coal-seams, we may
have only a very small part of the vegetable matter produced."
Undoubtedly the force of these reflections is not diminished when the
bituminous coal, as in Britain, consists of accumulated spores and
spore-cases, rather than of stems. But, suppose we adopt Principal
Dawson's assumption, that one foot of coal represents fifty
generations of coal plants; and, further, make the moderate
supposition that each generation of coal plants took ten years to come
to maturity--then, each foot-thickness of coal represents five hundred
years. The superimposed beds of coal in one coal-field may amount to
a thickness of fifty or sixty feet, and therefore the coal alone, in
that field, represents 500 x 50 = 25,000 years. But the actual coal is
but an insignificant portion of the total deposit, which, as has been
seen, may amount to between two and three miles of vertical thickness.
Suppose it be 12,000 feet--which is 240 times the thickness of the
actual coal--is there any reason why we should believe it may not have
taken 240 times as long to form? I know of none. But, in this case,
the time which the coal-field represents would be 25,000 x 240
=6,000,000 years. As affording a definite chronology, of course such
calculations as these are of no value; but they have much use in
fixing one's attention upon a possible minimum. A man may be puzzled
if he is asked how long Rome took a-building; but he is proverbially
safe if he affirms it not to have been built in a day; and our
geological calculations are all, at present, pretty much on that
footing.
A second consideration which the study of the coal brings prominently
before the mind of anyone who is familiar with palaeontology is, that
the coal Flora, viewed in relation to the enormous period of time
which it lasted, and to the still vaster period which has elapsed
since it flourished, underwent little change while it endured, and in
its peculiar characters, differs strangely little from that which at
present exists.
The same species of plants are to be met with throughout the whole
thickness of a coal-field, and the youngest are not sensibly different
from the oldest. But more than this. Notwithstanding that the
carboniferous period is separated from us by more than the whole time
represented by the secondary and tertiary formations, the great types
of vegetation were as distinct then as now. The structure of the
modern club-moss furnishes a complete explanation of the fossil
remains of the _Lepidodendra_, and the fronds of some of the ancient
ferns are hard to distinguish from existing ones. At the same time,
it must be remembered, that there is nowhere in the world, at present,
any _forest_ which bears more than a rough analogy with a coal-forest.
The types may remain, but the details of their form, their relative
proportions, their associates, are all altered. And the tree-fern
forest of Tasmania, or New Zealand, gives one only a faint and remote
image of the vegetation of the ancient world.
Once more, an invariably-recurring lesson of geological history,
at whatever point its study is taken up: the lesson of the almost
infinite slowness of the modification of living forms. The lines of
the pedigrees of living things break off almost before they begin to
converge.
Finally, yet another curious consideration. Let us suppose that one of
the stupid, salamander-like Labyrinthodonts, which pottered, with
much belly and little leg, like Falstaff in his old age, among the
coal-forests, could have had thinking power enough in his small brain
to reflect upon the showers of spores which kept on falling through
years and centuries, while perhaps not one in ten million fulfilled
its apparent purpose, and reproduced the organism which gave it birth:
surely he might have been excused for moralizing upon the thoughtless
and wanton extravagance which Nature displayed in her operations.
But we have the advantage over our shovel-headed predecessor--or
possibly ancestor--and can perceive that a certain vein of thrift runs
through this apparent prodigality. Nature is never in a hurry, and
seems to have had always before her eyes the adage, "Keep a thing long
enough, and you will find a use for it." She has kept her beds of coal
many millions of years without being able to find much use for them;
she has sent them down beneath the sea, and the sea-beasts could make
nothing of them; she has raised them up into dry land, and laid the
black veins bare, and still, for ages and ages, there was no living
thing on the face of the earth that could see any sort of value in
them; and it was only the other day, so to speak, that she turned a
new creature out of her workshop, who by degrees acquired sufficient
wits to make a fire, and then to discover that the black rock would
burn.
I suppose that nineteen hundred years ago, when Julius Caesar was good
enough to deal with Britain as we have dealt with New Zealand, the
primaeval Briton, blue with cold and woad, may have known that the
strange black stone, of which he found lumps here and there in his
wanderings, would burn, and so help to warm his body and cook his
food. Saxon, Dane, and Norman swarmed into the land. The English
people grew into a powerful nation, and Nature still waited for a full
return of the capital she had invested in the ancient club-mosses. The
eighteenth century arrived, and with it James Watt. The brain of that
man was the spore out of which was developed the steam-engine, and all
the prodigious trees and branches of modern industry which have grown
out of this. But coal is as much an essential condition of this growth
and development as carbonic acid is for that of a club-moss. Wanting
coal, we could not have smelted the iron needed to make our engines,
nor have worked our engines when we had got them. But take away the
engines, and the great towns of Yorkshire and Lancashire vanish like a
dream. Manufactures give place to agriculture and pasture, and not ten
men can live where now ten thousand are amply supported.
Thus, all this abundant wealth of money and of vivid life is Nature's
interest upon her investment in club-mosses, and the like, so long
ago. But what becomes of the coal which is burnt in yielding this
interest? Heat comes out of it, light comes out of it, and if we could
gather together all that goes up the chimney; and all that remains in
the grate of a thoroughly-burnt coal-fire, we should find ourselves in
possession of a quantity of carbonic acid, water, ammonia, and mineral
matters, exactly equal in weight to the coal. But these are the very
matters with which Nature supplied the club-mosses which made the
coal. She is paid back principal and interest at the same time; and
she straightway invests the carbonic acid, the water, and the ammonia
in new forms of life, feeding with them the plants that now live.
Thrifty Nature! Surely no prodigal, but most notable of housekeepers!
VI.
ON CORAL AND CORAL REEFS.
The marine productions which are commonly known by the names of
"Corals" and "Corallines," were thought by the ancients to be
sea-weeds, which had the singular property of becoming hard and
solid, when they were fished up from their native depths and came into
contact with the air.
"Sic et curalium, quo primum contigit auras Tempore durescit:
mollis fuit herba sub undis,"
says Ovid (Metam. xv.); and it was not until the seventeenth century
that Boccone was emboldened, by personal experience of the facts, to
declare that the holders of this belief were no better than "idiots,"
who had been misled by the softness of the outer coat of the living
red coral to imagine that it was soft all through.
Messer Boccone's strong epithet is probably undeserved, as the
notion he controverts, in all likelihood, arose merely from the
misinterpretation of the strictly true statement which any coral
fisherman would make to a curious inquirer; namely, that the outside
coat of the red coral is quite soft when it is taken out of the sea.
At any rate, he did good service by eliminating this much error from
the current notions about coral. But the belief that corals are plants
remained, not only in the popular, but in the scientific mind; and
it received what appeared to be a striking confirmation from the
researches of Marsigli in 1706. For this naturalist, having the
opportunity of observing freshly-taken red coral, saw that its
branches were beset with what looked like delicate and beautiful
flowers, each having eight petals. It was true that these "flowers"
could protrude and retract themselves, but their motions were hardly
more extensive, or more varied, than those of the leaves of the
sensitive plant; and therefore they could not be held to militate
against the conclusion so strongly suggested by their form and their
grouping upon the branches of a tree-like structure.
Twenty years later, a pupil of Marsigli, the young Marseilles
physician, Peyssonel, conceived the desire to study these singular
sea-plants, and was sent by the French Government on a mission to the
Mediterranean for that purpose. The pupil undertook the investigation
full of confidence in the ideas of his master, but being able to see
and think for himself, he soon discovered that those ideas by no means
altogether corresponded with reality. In an essay entitled "Traite du
Corail," which was communicated to the French Academy of Science, but
which has never been published, Peyssonel writes:--
"Je fis fleurir le corail dans des vases pleins d'eau de mer,
et j'observai que ce que nous croyons etre la fleur de cette
pretendue plante n'etait au vrai, qu'un insecte semblable a
une petite Ortie ou Poulpe. J'avais le plaisir de voir remuer
les pattes, ou pieds, de cette Ortie, et ayant mis le vase
plein d'eau ou le corail etait a une douce chaleur aupres
du feu, tous les petites insectes s'epanouirent ... L'Ortie
sortie etend les pieds, et forme ce que M. de Marsigli et moi
avions pris pour les petales de la fleur. Le calice de cette
pretendue fleur est le corps meme de l'animal avance et sorti
hors de la cellule."[1]
[Footnote 1: This extract from Peysonnel's manuscript is given by
M. Lacaze Duthiers in his valuable "Histoire Naturelle du Corail"
(1866).]
The comparison of the flowers of the coral to a "petite ortie" or
"little nettle" is perfectly just, but needs explanation. "Ortie de
mer," or "sea-nettle," is, in fact, the French appellation for our
"sea-anemone," a creature with which everybody, since the great
aquarium mania, must have become familiar, even to the limits of
boredom. In 1710, the great naturalist, Reaumur, had written a memoir
for the express purpose of demonstrating that these "orties" are
animals; and with this important paper Peyssonel must necessarily have
been familiar. Therefore, when he declared the "flowers" of the red
coral to be little "orties," it was the same thing as saying that
they were animals of the same general nature as sea-anemones. But
to Peyssonel's contemporaries this was an extremely startling
announcement. It was hard to imagine the existence of such a thing
as an association of animals into a structure with stem and branches
altogether like a plant, and fixed to the soil as a plant is fixed;
and the naturalists of that day preferred not to imagine it. Even
Reaumur could not bring himself to accept the notion, and France being
blessed with Academicians, whose great function (as the late Bishop
Wilson and an eminent modern writer have so well shown) is to cause
sweetness and light to prevail, and to prevent such unmannerly fellows
as Peyssonel from blurting out unedifying truths, they suppressed him;
and, as aforesaid, his great work remained in manuscript, and may
at this day be consulted by the curious in that state, in the
"Bibliotheque du Museum d'Histoire Naturelle." Peyssonel, who
evidently was a person of savage and untameable disposition, so far
from appreciating the kindness of the Academicians in giving him time
to reflect upon the unreasonableness, not to say rudeness, of making
public statements in opposition to the views of some of the most
distinguished of their body, seems bitterly to have resented the
treatment he met with. For he sent all further communications to the
Royal Society of London, which never had, and it is to be hoped never
will have, anything of an academic constitution; and finally took
himself off to Guadaloupe, and became lost to science altogether.
Fifteen or sixteen years after the date of Peyssonel's suppressed
paper, the Abbe Trembley published his wonderful researches upon the
fresh-water _Hydra_. Bernard de Jussieu and Guettard followed them
up by like inquiries upon the marine sea-anemones and corallines;
Reaumur, convinced against his will of the entire justice of
Peyssonel's views, adopted them, and made him a half-and-half apology
in the preface to the next published volume of the "Memoires pour
servir a l'Histoire des Insectes;" and, from this time forth,
Peyssonel's doctrine that corals are the work of animal organisms has
been part of the body of established scientific truth.
Peyssonel, in the extract from his memoir already cited, compares the
flower-like animal of the coral to a "poulpe," which is the French
form of the name "polypus,"--"the many-footed,"--which the ancient
naturalists gave to the soft-bodied cuttle-fishes, which, like the
coral animal, have eight arms, or tentacles, disposed around a central
mouth. Reaumur, admitting the analogy indicated by Peyssonel, gave the
name of _polypes_, not only to the sea-anemone, the coral animal, and
the fresh-water _Hydra_, but to what are now known as the _Polyzoa_,
and he termed the skeleton which they fabricate a "_polypier_" or
"polypidom."
The progress of discovery, since Reaumur's time, has made us very
completely acquainted with the structure and habits of all these
polypes. We know that, among the sea-anemones and coral-forming
animals, each polype has a mouth leading to a stomach, which is open
at its inner end, and thus communicates freely with the general cavity
of the body; that the tentacles placed round the mouth are hollow, and
that they perform the part of arms in seizing and capturing prey. It
is known that many of these creatures are capable of being multiplied
by artificial division, the divided halves growing, after a time, into
complete and separate animals; and that many are able to perform a
very similar process naturally, in such a manner that one polype may,
by repeated incomplete divisions, give rise to a sort of sheet,
or turf, formed by innumerable connected, and yet independent,
descendants. Or, what is still more common, a polype may throw out
buds, which are converted into polypes, or branches bearing polypes,
until a tree-like mass, sometimes of very considerable size, is
formed.
This is what happens in the case of the red coral of commerce. A
minute polype, fixed to the rocky bottom of the deep sea, grows up
into a branched trunk. The end of every branch and twig is terminated
by a polype; and all the polypes are connected together by a fleshy
substance, traversed by innumerable canals which place each polype in
communication with every other, and carry nourishment to the substance
of the supporting stem. It is a sort of natural co-operative store,
every polype helping the whole, at the same time as it helps itself.
The interior of the stem, like that of the branches, is solidified
by the deposition of carbonate of lime in its tissue, somewhat in the
same fashion as our own bones are formed of animal matter impregnated
with lime salts; and it is this dense skeleton (usually turned
deep red by a peculiar colouring matter) cleared of the soft animal
investment, as the heart-wood of a tree might be stripped of its bark,
which is the red coral.
In the case of the red coral, the hard skeleton belongs to the
interior of the stem and branches only; but in the commoner white
corals, each polype has a complete skeleton of its own. These
polypes ate sometimes solitary, in which case the whole skeleton is
represented by a single cup, with partitions radiating from its centre
to its circumference. When the polypes formed by budding or division
remain associated, the polypidom is sometimes made up of nothing but
an aggregation of these cups, while at other times the cups are at
once separated and held together, by an intermediate substance, which
represents the branches of the red coral. The red coral polype
again is a comparatively rare animal, inhabiting a limited area, the
skeleton of which has but a very insignificant mass; while the white
corals are very common, occur in almost all seas, and form skeletons
which are sometimes extremely massive.
With a very few exceptions, both the red and the white coral polypes
are, in their adult state, firmly adherent to the sea-bottom; nor do
their buds naturally become detached and locomotive. But, in addition
to budding and division, these creatures possess the more ordinary
methods of multiplication; and, at particular seasons, they give
rise to numerous eggs of minute size. Within these eggs the young are
formed, and they leave the egg in a condition which has no sort of
resemblance to the perfect animal. It is, in fact, a minute oval body,
many hundred times smaller than the full-grown creature, and it
swims about with great activity by the help of multitudes of little
hair-like filaments, called cilia, with which its body is covered.
These cilia all lash the water in one direction, and so drive the
little body along as if it were propelled by thousands of extremely
minute paddles. After enjoying its freedom for a longer or shorter
time, and being carried either by the force of its own cilia, or by
currents which bear it along, the embryo coral settles down to the
bottom, loses its cilia, and becomes fixed to the rock, gradually
assuming the polype form and growing up to the size of its parent.
As the infant polypes of the coral may retain this free and active
condition for many hours, or even days, and as a tidal or other
current in the sea may easily flow at the speed of two or even
more miles in an hour, it is clear that the embryo must often be
transported to very considerable distances from the parent. And it
is easily understood how a single polype, which may give rise to
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