being defined--that the class Rosaceae, for instance, or the class of
Fishes, is not accurately and absolutely definable, inasmuch as its
members will present exceptions to every possible definition; and that
the members of the class are united together only by the circumstance
that they are all more like some imaginary average rose or average
fish, than they resemble anything else.
But here, as before, I think the distinction has arisen entirely from
confusing a transitory imperfection with an essential character. So
long as our information concerning them is imperfect, we class all
objects together according to resemblances which we _feel_, but
cannot _define_; we group them round _types_, in short. Thus
if you ask an ordinary person what kinds of animals there are, he will
probably say, beasts, birds, reptiles, fishes, insects, &c. Ask him to
define a beast from a reptile, and he cannot do it; but he says, things
like a cow or a horse are beasts, and things like a frog or a lizard
are reptiles. You see _he does_ class by type, and not by definition.
But how does this classification differ from that of the
scientific Zoologist? How does the meaning of the scientific class-name
of "Mammalia" differ from the unscientific of "Beasts"?
Why, exactly because the former depends on a definition, the latter on
a type. The class Mammalia is scientifically defined as "all animals
which have a vertebrated skeleton and suckle their young." Here is no
reference to type, but a definition rigorous enough for a geometrician.
And such is the character which every scientific naturalist recognises
as that to which his classes must aspire--knowing, as he does, that
classification by type is simply an acknowledgment of ignorance and a
temporary device.
So much in the way of negative argument as against the reputed
differences between Biological and other methods. No such differences,
I believe, really exist. The subject-matter of Biological science is
different from that of other sciences, but the methods of all are
identical; and these methods are--
1. _Observation_ of facts--including under this head that _artificial
observation_ which is called _experiment_.
2. That process of tying up similar facts into bundles, ticketed and
ready for use, which is called _Comparison_ and _Classification_,--the
results of the process, the ticketed bundles, being named _General
propositions_.
3. _Deduction_, which takes us from the general proposition to facts
again--teaches us, if I may so say, to anticipate from the ticket
what is inside the bundle. And finally--
4. _Verification_, which is the process of ascertaining whether, in
point of fact, our anticipation is a correct one.
Such are the methods of all science whatsoever; but perhaps you will
permit me to give you an illustration of their employment in the
science of Life; and I will take as a special case the establishment of
the doctrine of the _Circulation of the Blood_.
In this case, _simple observation_ yields us a knowledge of the
existence of the blood from some accidental haemorrhage, we will say;
we may even grant that it informs us of the localisation of this blood
in particular vessels, the heart, &c., from some accidental cut or the
like. It teaches also the existence of a pulse in various parts of the
body, and acquaints us with the structure of the heart and vessels.
Here, however, _simple observation_ stops, and we must have recourse
to _experiment_.
You tie a vein, and you find that the blood accumulates on the side of
the ligature opposite the heart. You tie an artery, and you find that
the blood accumulates on the side near the heart. Open the chest, and
you see the heart contracting with great force. Make openings into its
principal cavities, and you will find that all the blood flows out, and
no more pressure is exerted on either side of the arterial or venous
ligature.
Now all these facts, taken together, constitute the evidence that the
blood is propelled by the heart through the arteries, and returns by
the veins--that, in short, the blood circulates.
Suppose our experiments and observations have been made on horses, then
we group and ticket them into a general proposition, thus:--_all
horses have a circulation of their blood_.
Henceforward a horse is a sort of indication or label, telling us where
we shall find a peculiar series of phaenomena called the circulation of
the blood.
Here is our _general proposition_, then.
How, and when, are we justified in making our next step--a _deduction_
from it?
Suppose our physiologist, whose experience is limited to horses, meets
with a zebra for the first time,--will he suppose that this
generalisation holds good for zebras also?
That depends very much on his turn of mind. But we will suppose him to
be a bold man. He will say, "The zebra is certainly not a horse, but it
is very like one,--so like, that it must be the 'ticket' or mark of a
blood-circulation also; and, I conclude that the zebra has a
circulation."
That is a deduction, a very fair deduction, but by no means to be
considered scientifically secure. This last quality in fact can only be
given by _verification_--that is, by making a zebra the subject of
all the experiments performed on the horse. Of course, in the present
case, the _deduction_ would be _confirmed_ by this process of
verification, and the result would be, not merely a positive widening
of knowledge, but a fair increase of confidence in the truth of one's
generalisations in other cases.
Thus, having settled the point in the zebra and horse, our philosopher
would have great confidence in the existence of a circulation in the
ass. Nay, I fancy most persons would excuse him, if in this case he did
not take the trouble to go through the process of verification at all;
and it would not be without a parallel in the history of the human
mind, if our imaginary physiologist now maintained that he was
acquainted with asinine circulation _à priori_.
However, if I might impress any caution upon your minds, it is, the
utterly conditional nature of all our knowledge,--the danger of
neglecting the process of verification under any circumstances; and the
film upon which we rest, the moment our deductions carry us beyond the
reach of this great process of verification. There is no better
instance of this than is afforded by the history of our knowledge of
the circulation of the blood in the animal kingdom until the year 1824.
In every animal possessing a circulation at all, which had been
observed up to that time, the current of the blood was known to take
one definite and invariable direction. Now, there is a class of animals
called _Ascidians_, which possess a heart and a circulation, and
up to the period of which I speak, no one would have dreamt of
questioning the propriety of the deduction, that these creatures have a
circulation in one direction; nor would any one have thought it worth
while to verify the point. But, in that year, M. von Hasselt, happening
to examine a transparent animal of this class, found, to his infinite
surprise, that after the heart had beat a certain number of times, it
stopped, and then began beating the opposite way--so as to reverse the
course of the current, which returned by and by to its original
direction.
I have myself timed the heart of these little animals. I found it as
regular as possible in its periods of reversal: and I know no spectacle
in the animal kingdom more wonderful than that which it presents--all
the more wonderful that to this day it remains an unique fact, peculiar
to this class among the whole animated world. At the same time I know
of no more striking case of the necessity of the _verification_ of
even those deductions which seem founded on the widest and safest
inductions.
Such are the methods of Biology--methods which are obviously identical
with those of all other sciences, and therefore wholly incompetent to
form the ground of any distinction between it and them. [5]
But I shall be asked at once, Do you mean to say that there is no
difference between the habit of mind of a mathematician and that of a
naturalist? Do you imagine that Laplace might have been put into the
Jardin des Plantes, and Cuvier into the Observatory, with equal
advantage to the progress of the sciences they professed?
To which I would reply, that nothing could be further from my thoughts.
But different habits and various special tendencies of two sciences do
not imply different methods. The mountaineer and the man of the plains
have very different habits of progression, and each would be at a loss
in the other's place; but the method of progression, by putting one leg
before the other, is the same in each case. Every step of each is a
combination of a lift and a push; but the mountaineer lifts more and
the lowlander pushes more. And I think the case of two sciences
resembles this.
I do not question for a moment, that while the Mathematician is busy
with deductions _from_ general propositions, the Biologist is more
especially occupied with observation, comparison, and those processes
which lead _to_ general propositions. All I wish to insist upon
is, that this difference depends not on any fundamental distinction in
the sciences themselves, but on the accidents of their subject-matter,
of their relative complexity, and consequent relative perfection.
The Mathematician deals with two properties of objects only, number and
extension, and all the inductions he wants have been formed and
finished ages ago. He is occupied now with nothing but deduction and
verification.
The Biologist deals with a vast number of properties of objects, and
his inductions will not be completed, I fear, for ages to come; but
when they are, his science will be as deductive and as exact as the
Mathematics themselves.
Such is the relation of Biology to those sciences which deal with
objects having fewer properties than itself. But as the student, in
reaching Biology, looks back upon sciences of a less complex and
therefore more perfect nature; so, on the other hand, does he look
forward to other more complex and less perfect branches of knowledge.
Biology deals only with living beings as isolated things--treats only
of the life of the individual: but there is a higher division of
science still, which considers living beings as aggregates--which deals
with the relation of living beings one to another--the science which
_observes_ men--whose _experiments_ are made by nations one
upon another, in battlefields--whose _general propositions_ are
embodied in history, morality, and religion--whose _deductions_
lead to our happiness or our misery--and whose _verifications_ so
often come too late, and serve only
"To point a moral, or adorn a tale"--
I mean the science of Society or _Sociology_.
I think it is one of the grandest features of Biology, that it occupies
this central position in human knowledge. There is no side of the human
mind which physiological study leaves uncultivated. Connected by
innumerable ties with abstract science, Physiology is yet in the most
intimate relation with humanity; and by teaching us that law and order,
and a definite scheme of development, regulate even the strangest and
wildest manifestations of individual life, she prepares the student to
look for a goal even amidst the erratic wanderings of mankind, and to
believe that history offers something more than an entertaining
chaos--a journal of a toilsome, tragi-comic march no-whither.
The preceding considerations have, I hope, served to indicate the
replies which befit the first two of the questions which I set before
you at starting, viz. What is the range and position of Physiological
Science as a branch of knowledge, and what is its value as a means of
mental discipline?
Its _subject-matter_ is a large moiety of the universe--its
_position_ is midway between the physico-chemical and the social
sciences. Its _value_ as a branch of discipline is partly that
which it has in common with all sciences--the training and
strengthening of common sense; partly that which is more peculiar to
itself--the great exercise which it affords to the faculties of
observation and comparison; and, I may add, the _exactness_ of
knowledge which it requires on the part of those among its votaries who
desire to extend its boundaries.
If what has been said as to the position and scope of Biology be
correct, our third question--What is the practical value of
physiological instruction?--might, one would think, be left to answer
itself.
On other grounds even, were mankind deserving of the title "rational,"
which they arrogate to themselves, there can be no question that they
would consider, as the most necessary of all branches of instruction
for themselves and for their children, that which professes to acquaint
them with the conditions of the existence they prize so highly--which
teaches them how to avoid disease and to cherish health, in themselves
and those who are dear to them.
I am addressing, I imagine, an audience of educated persons; and yet I
dare venture to assert that, with the exception of those of my hearers
who may chance to have received a medical education, there is not one
who could tell me what is the meaning and use of an act which he
performs a score of times every minute, and whose suspension would
involve his immediate death;--I mean the act of breathing--or who could
state in precise terms why it is that a confined atmosphere is
injurious to health.
The _practical value_ of Physiological knowledge! Why is it that
educated men can be found to maintain that a slaughter-house in the
midst of a great city is rather a good thing than otherwise?--that
mothers persist in exposing the largest possible amount of surface of
their children to the cold, by the absurd style of dress they adopt,
and then marvel at the peculiar dispensation of Providence, which
removes their infants by bronchitis and gastric fever? Why is it that
quackery rides rampant over the land; and that not long ago, one of the
largest public rooms in this great city could be filled by an audience
gravely listening to the reverend expositor of the doctrine--that the
simple physiological phaenomena known as spirit-rapping, table-turning,
phreno-magnetism, and I know not what other absurd and inappropriate
names, are due to the direct and personal agency of Satan?
Why is all this, except from the utter ignorance as to the simplest
laws of their own animal life, which prevails among even the most
highly educated persons in this country?
But there are other branches of Biological Science, besides Physiology
proper, whose practical influence, though less obvious, is not, as I
believe, less certain. I have heard educated men speak with an
ill-disguised contempt of the studies of the naturalist, and ask, not
without a shrug, "What is the use of knowing all about these miserable
animals--what bearing has it on human life?"
I will endeavour to answer that question. I take it that all will admit
there is definite Government of this universe--that its pleasures and
pains are not scattered at random, but are distributed in accordance
with orderly and fixed laws, and that it is only in accordance with all
we know of the rest of the world, that there should be an agreement
between one portion of the sensitive creation and another in these
matters.
Surely then it interests us to know the lot of other animal
creatures--however far below us, they are still the sole created things
which share with us the capability of pleasure and the susceptibility
to pain.
I cannot but think that he who finds a certain proportion of pain and
evil inseparably woven up in the life of the very worms, will bear his
own share with more courage and submission; and will, at any rate, view
with suspicion those weakly amiable theories of the Divine government,
which would have us believe pain to be an oversight and a mistake,--to
be corrected by and by. On the other hand, the predominance of
happiness among living things--their lavish beauty--the secret and
wonderful harmony which pervades them all, from the highest to the
lowest, are equally striking refutations of that modern Manichean
doctrine, which exhibits the world as a slave-mill, worked with many
tears, for mere utilitarian ends.
There is yet another way in which natural history may, I am convinced,
take a profound hold upon practical life,--and that is, by its
influence over our finer feelings, as the greatest of all sources of
that pleasure which is derivable from beauty. I do not pretend that
natural-history knowledge, as such, can increase our sense of the
beautiful in natural objects. I do not suppose that the dead soul of
Peter Bell, of whom the great poet of nature says,--
A primrose by the river's brim,
A yellow primrose was to him,--
And it was nothing more,--
would have been a whit roused from its apathy by the information that
the primrose is a Dicotyledonous Exogen, with a monopetalous corolla
and central placentation. But I advocate natural-history knowledge from
this point of view, because it would lead us to _seek_ the
beauties of natural objects, instead of trusting to chance to force
them on our attention. To a person uninstructed in natural history, his
country or sea-side stroll is a walk through a gallery filled with
wonderful works of art, nine-tenths of which have their faces turned to
the wall. Teach him something of natural history, and you place in his
hands a catalogue of those which are worth turning round. Surely our
innocent pleasures are not so abundant in this life, that we can afford
to despise this or any other source of them. We should fear being
banished for our neglect to that limbo, where the great Florentine
tells us are those who, during this life, "wept when they might be
joyful."
But I shall be trespassing unwarrantably on your kindness, if I do not
proceed at once to my last point--the time at which Physiological
Science should first form a part of the Curriculum of Education.
The distinction between the teaching of the facts of a science as
instruction, and the teaching it systematically as knowledge, has
already been placed before you in a previous lecture: and it appears to
me that, as with other sciences, the _common facts_ of Biology--the
uses of parts of the body--the names and habits of the living
creatures which surround us--may be taught with advantage to the
youngest child. Indeed, the avidity of children for this kind of
knowledge, and the comparative ease with which they retain it, is
something quite marvellous. I doubt whether any toy would be so
acceptable to young children as a vivarium of the same kind as, but of
course on a smaller scale than, those admirable devices in the
Zoological Gardens.
On the other hand, systematic teaching in Biology cannot be attempted
with success until the student has attained to a certain knowledge of
physics and chemistry: for though the phaenomena of life are dependent
neither on physical nor on chemical, but on vital forces, yet they
result in all sorts of physical and chemical changes, which can only be
judged by their own laws.
And now to sum up in a few words the conclusions to which I hope you
see reason to follow me.
Biology needs no apologist when she demands a place--and a prominent
place--in any scheme of education worthy of the name. Leave out the
Physiological sciences from your curriculum, and you launch the student
into the world, undisciplined in that science whose subject-matter
would best develop his powers of observation; ignorant of facts of the
deepest importance for his own and others' welfare; blind to the
richest sources of beauty in God's creation; and unprovided with that
belief in a living law, and an order manifesting itself in and through
endless change and variety, which might serve to check and moderate
that phase of despair through which, if he take an earnest interest in
social problems, he will assuredly sooner or later pass.
Finally, one word for myself. I have not hesitated to speak strongly
where I have felt strongly; and I am but too conscious that the
indicative and imperative moods have too often taken the place of the
more becoming subjunctive and conditional. I feel, therefore, how
necessary it is to beg you to forget the personality of him who has
thus ventured to address you, and to consider only the truth or error
in what has been said.
* * * * *
Footnotes:
[1] "In the third place, we have to review the method of Comparison,
which is so specially adapted to the study of living bodies, and by
which, above all others, that study must be advanced. In Astronomy,
this method is necessarily inapplicable; and it is not till we arrive
at Chemistry that this third means of investigation can be used, and
then only in subordination to the two others. It is in the study, both
statical and dynamical, of living bodies that it first acquires its
full development; and its use elsewhere can be only through its
application here."--COMTE'S _Positive Philosophy_, translated by
Miss Martineau. Vol. i. p. 372.
By what method does M. Comte suppose that the equality or inequality
of forces and quantities and the dissimilarity or similarity of
forms--points of some slight importance not only in Astronomy and
Physics, but even in Mathematics--are ascertained, if not by
Comparison?
[2] "Proceeding to the second class of means,--Experiment cannot but be
less and less decisive, in proportion to the complexity of the
phaenomena to be explored; and therefore we saw this resource to be
less effectual in chemistry than in physics: and we now find that it is
eminently useful in chemistry in comparison with physiology. _In
fact, the nature of the phenomena seems to offer almost insurmountable
impediments to any extensive and prolific application of such a
procedure in biology._"--COMTE, vol. i. p. 367.
M. Comte, as his manner is, contradicts himself two pages further on,
but that will hardly relieve him from the responsibility of such a
paragraph as the above.
[3] _Nouvelle Fonction du Foie considéré comme organe producteur de
matière sucrée chez l'Homme et les Animaux, par_ M. Claude Bernard.
[4] "_Natural Groups given by Type, not by Definition_.... The
class is steadily fixed, though not precisely limited; it is given,
though not circumscribed; it is determined, not by a boundary-line
without, but by a central point within; not by what it strictly
excludes, but what it eminently includes; by an example, not by a
precept; in short, instead of Definition we have a _Type_ for our
director. A type is an example of any class, for instance, a species of
a genus, which is considered as eminently possessing the characters of
the class. All the species which have a greater affinity with this
type-species than with any others, form the genus, and are ranged about
about it, deviating from it in various directions and different
degrees."--WHEWELL, _The Philosophy of the Inductive Sciences_,
vol. i. pp. 476, 477.
[5] Save for the pleasure of doing so, I need hardly point put my
obligations to Mr. J. S. Mill's _System of Logic_, in this view of
scientific method.
III
EMANCIPATION--BLACK AND WHITE
[1865.]
Quashie's plaintive inquiry, "Am I not a man and a brother?" seems at
last to have received its final reply--the recent decision of the
fierce trial by battle on the other side of the Atlantic fully
concurring with that long since delivered here in a more peaceful way.