The subject to which I have to beg your attention during the ensuing hour is "The Relation of Physiological Science to other branches of knowledge."
Had circumstances permitted of the delivery, in their strict logical order, of that series of discourses of which the present lecture is a member, I should have preceded my friend and colleague Mr. Henfrey, who addressed you on Monday last; but while, for the sake of that order, I must beg you to suppose that this discussion of the Educational bearings of Biology in general does precede that of Special Zoology and Botany, I am rejoiced to be able to take advantage of the light thus already thrown upon the tendency and methods of Physiological Science.
Regarding Physiological Science, then, in its  widest senseas the equivalent of Biologythe Science of Individual Lifewe have to consider in succession:
1. Its position and scope as a branch of knowledge.
2. Its value as a means of mental discipline.
3. Its worth as practical information. And lastly,
4. At what period it may best be made a branch of Education.
Our conclusions on the first of these heads must depend, of course, upon the nature of the subject-matter of Biology; and I think a few preliminary considerations will place before you in a clear light the vast difference which exists between the living bodies with which Physiological Science is concerned, and the remainder of the universe;between the phænomena of Number and Space, of Physical and of Chemical force, on the one hand, and those of Life on the other.
The mathematician, the physicist, and the chemist contemplate things in a condition of rest; they look upon a state of equilibrium as that to which all bodies normally tend.
The mathematician does not suppose that a quantity will alter, or that a given point in space will change its direction with regard to another point, spontaneously. And it is the same with the physicist. When Newton saw the apple fall,  he concluded at once that the act of falling was not the result of any power inherent in the apple, but that it was the result of the action of something else on the apple. In a similar manner, all physical force is regarded as the disturbance of an equilibrium to which things tended before its exertion,to which they will tend again after its cessation.
The chemist equally regards chemical change in a body as the effect of the action of something external to the body changed. A chemical compound once formed would persist for ever, if no alteration took place in surrounding conditions.
But to the student of Life the aspect of Nature is reversed. Here, incessant, and, so far as we know, spontaneous change is the rule, rest the exceptionthe anomaly to be accounted for. Living things have no inertia, and tend to no equilibrium.
Permit me, however, to give more force and clearness to these somewhat abstract considerations by an illustration or two.
Imagine a vessel full of water, at the ordinary temperature, in an atmosphere saturated with vapour. The quantity and the figure of that water will not change, so far as we know, for ever.
Suppose a lump of gold be thrown into the vesselmotion and disturbance of figure exactly proportional to the momentum of the gold will take  place. But after a time the effects of this disturbance will subsideequilibrium will be restored, and the water will return to its passive state.
Expose the water to coldit will solidifyand in so doing its particles will arrange themselves in definite crystalline shapes. But once formed, these crystals change no further.
Again, substitute for the lump of gold some substance capable of entering into chemical relations with the water:say, a mass of that substance which is called "protein"the substance of flesh:a very considerable disturbance of equilibrium will take placeall sorts of chemical compositions and decompositions will occur; but in the end, as before, the result will be the resumption of a condition of rest.
Instead of such a mass of dead protein, however, take a particle of living proteinone of those minute microscopic living things which throng our pools, and are known as Infusoriasuch a creature, for instance, as an Euglena, and place it in our vessel of water. It is a round mass provided with a long filament, and except in this peculiarity of shape, presents no appreciable physical or chemical difference whereby it might be distinguished from the particle of dead protein.
But the difference in the phænomena to which it will give rise is immense: in the first place it will develop a vast quantity of physical forcecleaving the water in all directions with considerable rapidity by means of the vibrations of the long filament of cilium.
Nor is the amount of chemical energy which the little creature possesses less striking. It is a perfect laboratory in itself, and it will act and react upon the water and the matters contained therein; converting them into new compounds resembling its own substance, and at the same time giving up portions of its own substance which have become effete.
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 assumes 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 assume a totally new form, lose their long tailsround 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 reststhe particle of dead protein decomposes and disappearsit also rests: but the living protein mass 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 livethe domain of the chemist and physicist.
Tendency to disturb existing equilibriumto take on forms which succeed one another in definite cyclesis 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 casesvery possibly they will find out some bond between physico-chemical phænomena on the one hand, and vital phænomena on the other. At present, however, we assuredly know of none; and I think we shall exercise a wise humility in confessing that, for us at least, this successive assumption of different states(external conditions  remaining the same)that spontaneity of action if I may use the term which implies more than I would be answerable forwhich constitutes 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 constituted by perhaps not more than two or three steps in the Euglena, is as clearly manifested in the multitudinous stages through which the germ of an oak or of a man passes. Whatever forms the Living Being may take on, whether simple or complex, production, growth, reproduction, are the phænomena which distinguish it from that which does not live.
If this be true, it is clear that the student, in passing 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 methodmust be as truly a man of scienceas 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 when 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 saidand I take this point first, because the imputation is too frequently admitted by Physiologists themselvesthat 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 downI 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 multitude of interfering conditions, we are very often only enabled to predict approximately what will occur under given circumstances; 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 classification have been misled by the accident of the name of one leading branch of BiologyComparative Anatomy; but I would ask whether comparison, and that classification 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 assertions 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 nerve, save by experiment? How do we know the use of a nerve at all, except by experiment? Nay, how do we 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 classification takes place by type and not by definition.4
It is said, in short, that a natural-history class is not capable of being definedthat the class  Rosaceæ, 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 a 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 aspireknowing, 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 factsincluding 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 againteaches 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 hæmorrhage, 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 veinsthat, 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 phænomena called the circulation of the blood.
Here is our general proposition, then.
How, and when, are we justified in making our next stepa 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 verificationthat 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 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 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 wayso 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 presentsall 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 Biologymethods 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 thingstreats only of the life of the individual: but there is a higher division of science still, which considers living beings as aggregateswhich deals with the relation of living beings one to anotherthe science which observes menwhose experiments are made by nations one upon another, in battle-fieldswhose general propositions are embodied in history, morality, and religionwhose deductions lead to our happiness or our miseryand 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 chaosa 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 universeits 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 sciencesthe training and strengthening of common sense; partly that which is more peculiar to itselfthe 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 questionWhat 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 highlywhich 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 breathingor 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 doctrinethat the simple physiological phænomena 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 animalswhat 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 universethat 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 creatureshowever 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 thingstheir lavish beautythe 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 pointthe 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 Biologythe uses of parts of the bodythe names and habits of the living creatures which surround usmay 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 phænomena 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 placeand a prominent placein 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.
"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 formspoints out some slight importance not only in Astronomy and Physics, but even in Mathematicsare ascertained, if not by Comparison? 2
"Proceeding to the second class of meansExperiment cannot but be less and less decisive, in proportion to the complexity of the phænomena 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 phænomena seems to offer almost insurmountable impediments to any extensive and prolific application of such a procedure in biology."Comte, vol. 1, 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 matiére sucrée chez l'Homme et les Animalaux, 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 aType 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 it, deviating from it in various directions and different degrees."Whewell, The Philosophy of the Inductive Sciences, vol. 12, pp. 476, 477. 5
Save for the pleasure of doing so, I need hardly point out my obligations to Mr. J. S. Mill's System of Logic, in this view of scientific method.
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 formspoints out some slight importance not only in Astronomy and Physics, but even in Mathematicsare ascertained, if not by Comparison?
2 "Proceeding to the second class of meansExperiment cannot but be less and less decisive, in proportion to the complexity of the phænomena 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 phænomena seems to offer almost insurmountable impediments to any extensive and prolific application of such a procedure in biology."Comte, vol. 1, 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 matiére sucrée chez l'Homme et les Animalaux, 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 aType 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 it, deviating from it in various directions and different degrees."Whewell, The Philosophy of the Inductive Sciences, vol. 12, pp. 476, 477.
5 Save for the pleasure of doing so, I need hardly point out my obligations to Mr. J. S. Mill's System of Logic, in this view of scientific method.
Preface and Table of Contents to Volume III, Science & Education, of Huxley's Collected Essays.
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