Science and Education: Essays Part 3

Furthermore, the Euglena will increase in size; but this increase is by no means unlimited, as the increase of a crystal might be. After it has grown to a certain extent it divides, and each portion a.s.sumes the form of the original, and proceeds to repeat the process of growth and division.

Nor is this all. For after a series of such divisions and subdivisions, these minute points a.s.sume a totally new form, lose their long tails--round themselves, and secrete a sort of envelope or box, in which they remain shut up for a time, eventually to resume, directly or indirectly, their primitive mode of existence.

Now, so far as we know, there is no natural limit to the existence of the Euglena, or of any other living germ. A living species once launched into existence tends to live for ever.

Consider how widely different this living particle is from the dead atoms with which the physicist and chemist have to do!

The particle of gold falls to the bottom and rests--the particle of dead protein decomposes and disappears--it also rests: but the _living_ protein ma.s.s neither tends to exhaustion of its forces nor to any permanency of form, but is essentially distinguished as a disturber of equilibrium so far as force is concerned,--as undergoing continual metamorphosis and change, in point of form.

Tendency to equilibrium of force and to permanency of form, then, are the characters of that portion of the universe which does not live--the domain of the chemist and physicist.

Tendency to disturb existing equilibrium--to take on forms which succeed one another in definite cycles--is the character of the living world.

What is the cause of this wonderful difference between the dead particle and the living particle of matter appearing in other respects identical? that difference to which we give the name of Life?

I, for one, cannot tell you. It may be that, by and by, philosophers will discover some higher laws of which the facts of life are particular cases--very possibly they will find out some bond between physico-chemical phaenomena on the one hand, and vital phaenomena on the other. At present, however, we a.s.suredly know of none; and I think we shall exercise a wise humility in confessing that, for us at least, this successive a.s.sumption of different states--(external conditions remaining the same)--this _spontaneity of action_--if I may use a term which implies more than I would be answerable for--which const.i.tutes so vast and plain a practical distinction between living bodies and those which do not live, is an ultimate fact; indicating as such, the existence of a broad line of demarcation between the subject-matter of Biological and that of all other sciences.

For I would have it understood that this simple Euglena is the type of _all_ living things, so far as the distinction between these and inert matter is concerned. That cycle of changes, which is const.i.tuted by perhaps not more than two or three steps in the Euglena, is as clearly manifested in the mult.i.tudinous stages through which the germ of an oak or of a man pa.s.ses. Whatever forms the Living Being may take on, whether simple or complex, _production, growth, reproduction,_ are the phaenomena which distinguish it from that which does not live.

If this be true, it is clear that the student, in pa.s.sing from the physico-chemical to the physiological sciences, enters upon a totally new order of facts; and it will next be for us to consider how far these new facts involve _new_ methods, or require a modification of those with which he is already acquainted. Now a great deal is said about the peculiarity of the scientific method in general, and of the different methods which are pursued in the different sciences. The Mathematics are said to have one special method; Physics another, Biology a third, and so forth. For my own part, I must confess that I do not understand this phraseology.

So far as I can arrive at any clear comprehension of the matter, Science is not, as many would seem to suppose, a modification of the black art, suited to the tastes of the nineteenth century, and flourishing mainly in consequence of the decay of the Inquisition.

Science is, I believe, nothing but _trained and organised common sense_, differing from the latter only as a veteran may differ from a raw recruit: and its methods differ from those of common sense only so far as the guardsman's cut and thrust differ from the manner in which a savage wields his club. The primary power is the same in each case, and perhaps the untutored savage has the more brawny arm of the two. The _real_ advantage lies in the point and polish of the swordsman's weapon; in the trained eye quick to spy out the weakness of the adversary; in the ready hand prompt to follow it on the instant.

But, after all, the sword exercise is only the hewing and poking of the clubman developed and perfected.

So, the vast results obtained by Science are won by no mystical faculties, by no mental processes, other than those which are practised by every one of us, in the humblest and meanest affairs of life. A detective policeman discovers a burglar from the marks made by his shoe, by a mental process identical with that by which Cuvier restored the extinct animals of Montmartre from fragments of their bones. Nor does that process of induction and deduction by which a lady, finding a stain of a peculiar kind upon her dress, concludes that somebody has upset the inkstand thereon, differ in any way, in kind, from that by which Adams and Leverrier discovered a new planet.

The man of science, in fact, simply uses with scrupulous exactness the methods which we all, habitually and at every moment, use carelessly; and the man of business must as much avail himself of the scientific method--must be as truly a man of science--as the veriest bookworm of us all; though I have no doubt that the man of business will find himself out to be a philosopher with as much surprise as M. Jourdain exhibited vhen he discovered that he had been all his life talking prose. If, however, there be no real difference between the methods of science and those of common life, it would seem, on the face of the matter, highly improbable that there should be any difference between the methods of the different sciences; nevertheless, it is constantly taken for granted that there is a very wide difference between the Physiological and other sciences in point of method.

In the first place it is said--and I take this point first, because the imputation is too frequently admitted by Physiologists themselves--that Biology differs from the Physico-chemical and Mathematical sciences in being "inexact."

Now, this phrase "inexact" must refer either to the _methods_ or to the _results_ of Physiological science.

It cannot be correct to apply it to the methods; for, as I hope to show you by and by, these are identical in all sciences, and whatever is true of Physiological method is true of Physical and Mathematical method.

Is it then the _results_ of Biological science which are "inexact"?

I think not. If I say that respiration is performed by the lungs; that digestion is effected in the stomach; that the eye is the organ of sight; that the jaws of a vertebrated animal never open sideways, but always up and down; while those of an annulose animal always open sideways, and never up and down--I am enumerating propositions which are as exact as anything in Euclid. How then has this notion of the inexactness of Biological science come about? I believe from two causes: first, because in consequence of the great complexity of the science and the mult.i.tude of interfering conditions, we are very often only enabled to predict approximately what will occur under given circ.u.mstances; and secondly, because, on account of the comparative youth of the Physiological sciences, a great many of their laws are still imperfectly worked out. But, in an educational point of view, it is most important to distinguish between the essence of a science and the accidents which surround it; and essentially, the methods and results of Physiology are as exact as those of Physics or Mathematics.

It is said that the Physiological method is especially _comparative_; [1] and this dictum also finds favour in the eyes of many.

I should be sorry to suggest that the speculators on scientific cla.s.sification have been misled by the accident of the name of one leading branch of Biology--_Comparative Anatomy_; but I would ask whether _comparison_, and that cla.s.sification which is the result of comparison, are not the essence of every science whatsoever? How is it possible to discover a relation of cause and effect of _any_ kind without comparing a series of cases together in which the supposed cause and effect occur singly, or combined? So far from comparison being in any way peculiar to Biological science, it is, I think, the essence of every science.

A speculative philosopher again tells us that the Biological sciences are distinguished by being sciences of observation and not of experiment! [2] Of all the strange a.s.sertions into which speculation without practical acquaintance with a subject may lead even an able man, I think this is the very strangest. Physiology not an experimental science? Why, there is not a function of a single organ in the body which has not been determined wholly and solely by experiment? How did Harvey determine the nature of the circulation, except by experiment?

How did Sir Charles Bell determine the functions of the roots of the spinal nerves, save by experiment? How do we know the use of a nerve at all, except by experiment? Nay, how do you know even that your eye is your seeing apparatus, unless you make the experiment of shutting it; or that your ear is your hearing apparatus, unless you close it up and thereby discover that you become deaf?

It would really be much more true to say that Physiology is _the_ experimental science _par excellence_ of all sciences; that in which there is least to be learnt by mere observation, and that which affords the greatest field for the exercise of those faculties which characterise the experimental philosopher. I confess, if any one were to ask me for a model application of the logic of experiment, I should know no better work to put into his hands than Bernard's late Researches on the Functions of the Liver. [3]

Not to give this lecture a too controversial tone, however, I must only advert to one more doctrine, held by a thinker of our own age and country, whose opinions are worthy of all respect. It is, that the Biological sciences differ from all others, inasmuch as in _them_ cla.s.sification takes place by type and not by definition. [4]

It is said, in short, that a natural-history cla.s.s is not capable of being defined--that the cla.s.s Rosaceae, for instance, or the cla.s.s 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 cla.s.s are united together only by the circ.u.mstance 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 cla.s.s 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_ cla.s.s by type, and not by definition.

But how does this cla.s.sification differ from that of the scientific Zoologist? How does the meaning of the scientific cla.s.s-name of "Mammalia" differ from the unscientific of "Beasts"?

Why, exactly because the former depends on a definition, the latter on a type. The cla.s.s 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 cla.s.ses must aspire--knowing, as he does, that cla.s.sification 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 _Cla.s.sification_,--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 antic.i.p.ate from the ticket what is inside the bundle. And finally--

4. _Verification_, which is the process of ascertaining whether, in point of fact, our antic.i.p.ation is a correct one.

Such are the methods of all science whatsoever; but perhaps you will permit me to give you an ill.u.s.tration 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 acc.u.mulates on the side of the ligature opposite the heart. You tie an artery, and you find that the blood acc.u.mulates on the side near the heart. Open the chest, and you see the heart contracting with great force. Make openings into its princ.i.p.al 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, const.i.tute 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 a.s.s. 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 _a 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 circ.u.mstances; 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 cla.s.s 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 Ha.s.selt, happening to examine a transparent animal of this cla.s.s, 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 cla.s.s 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.