362 



NA TURE 



\Sept. 3, 1874 



ON THE HYPOTHESIS THAT ANIMALS ARE 

 AUTOMATA, AND ITS HISTORY* 



A T this period of the meetiii'j of the British Association I am 

 -'*- quite sure it is hardly necessary for me to call to your minds 

 *he nature of the business which takes place at our sectional meet- 

 'ngs. We there register the progress which science has made during 

 the past year, and we do our best to advance that progress by 

 oriqinal communications and free discussion. But when the 

 honourable task of delivering this evening's lecture was im- 

 posed upon me, or rather as my friend the President has just 

 said, when I undertook to deliver it, it occurred to me that the 

 occasion of an evening lecture might be turned to a different 

 purpose, that we might with much propriety and advantage turn 

 our minds back to the past to consider what had been done by 

 the great men of old, who "had gone down into the grave with 

 their weapons of war," but who had fought bravely for the cause 

 of truth while they yet lived- to recognise their merits, and to 

 show ourselves duly grateful for their services. I propose, there- 

 fore, to take a retrospect of the condition of that branch of science 

 ivith which it is my business to be more or less familiar — not 

 to a very remote period, for I shall go no fuither back than tlie 

 seventeenth century, and the observations which 1 shall have to 

 offer you will be confined almost entirely to the biological science 

 of the time between the middle of the seventeenth and the middle 

 of the eighteenth centuries. I propose to show what great 

 ideas in biological science took their origin at that time, in what 

 manner the speculations then originated have been developed, 

 and in what relation they stand to what is now understood to be 

 the body of scientific biological truth. The middle of the 

 sixteenth century, or rather the early part of it, is one of the 

 great epochs of biological science. It was at that time that an 

 idea, which had been dimly advocated previously, took the solid 

 form which can only lie given to scientific ideas by the definite 

 observation of fact — I mean the idea that vital phenomena, like 

 all other phenomena of the physical world, are capable of 

 mechanical explanation, that they are reducible to law and 

 order, and that the study of biology, in the long run, is an 

 application of the great sciences of physics and chemistry. The 

 man to whom we are indebted for first bringing that idea into a 

 plain and tangible shape, I am proud to say, was an Englishman, 

 William Harvey. Harvey was the first clearly to explain the 

 mechanism of the circulation of the blood, and lay that remark- 

 able discovery of his, and by the clearness and precision with 

 which he reduced that process to its mechanical elements, he 

 laid the foundation of a scientific theory of the larger part of the 

 processes of living beings — those processes, in fact, which we 

 now call processes of sustentation — and by his studies of de- 

 velopment he, further, first laid the foundation of a scientific 

 knowledge of reproduction. But besides these great powers of 

 living beings, there remains another class of functions — those of 

 the nervoui system — with which Harvey did not grapple. It 

 was, indeed left for a contemporary of his, a man who, as he 

 hmself tel's us, was mainly stimulated in these inquiries by 

 the brilliant researches of Harvey — Riine Descartes— to play 

 a part in relation to the phenomena of the nervous system, 

 which, in my judgment, is equal in value to that which Harvey 

 played in regird to the circulation. And when we consider who 

 Descar;es was, how brief the span of his life, 1 think it is a 

 truly wonderful circumstance that this man, who died at fifty- 

 four, should be one of the recognised leaders of philosophy — 

 Ihit, as I am informed by competent autnority, he was one of 

 the first and most original mathematicians who lias ever lived, 

 and that, at the same time, the fertility of his intellect and the 

 grasp of his genius should have been so great that he could take 

 rank, as I believe he must, beside the immortal Harvey as a 

 physiologist. An 1 you must recollect that Descartes was not 

 rarely, as some had been, a happy speculator. He was a 

 working anatomi t and physiologist, conversant with all the 

 anatomical and physiological lore of his time, and practised in 

 all methods by which anatomical and physiological discoveries 

 «eie then made ; and it is rela;ed of him — and a most charac- 

 teristic anecdote it is, and one which should ever put to silence 

 those shallow talkers who speak of Descartes as a merely 

 hypothetical and speculative philosopher — that a friend once 

 railing upon him in Holland begged to be shown his library. 

 Descaites led him into a sort of sited, and, drawing aside a 

 curtain, displayed a dissecting-room full of bodies of animals in 

 course of dissection, and said, "There is my library." It would 



• Address by I ruf. IIuvlcv, F US.. ,it the Irilish Associ. lion, I'.cir.isl. 



take us a very long time if I were to attempt to pursue the method 

 which would be requisite for the full establishment of all that 

 I am about to say ; that is to say, if I were to quote the several 

 passages of Descartess works which bear out my ascription to 

 him of the several propositions which I am going to bring 

 before you. And I must beg you, therefore, to be so good 

 as to take it on my authority for the present, although for 

 the present only, that there are to be found clearly expressed 

 in Descartes' works the propositions which I shall proceed 

 to lay before you, and each of which I shall compare as 

 we go on, as briefly as may be, with the existing state of 

 physiological science, in order that you may see in what position 

 with respect to physiology — ay, even to the advanced physiology 

 of the present time — this man stood. And, happily, the matters 

 with which we shall treat are such as to require no extensive 

 knowledge of anatomy — no more, in fact, than such as, I pre- 

 sume, must be familiar to almost every person. 



I think I need only premise that what we call the nervaus 

 system in one of the higher animals consists of a central apparatus, 

 composed of the brain, which is lodged in the skull, and ef a 

 cord jjioceedinj; from it, which is termed the spinal marrow, 

 and which is lodged in the vertebral column or spine, and 

 that from these soft white masses — for such they are — 

 there proceed cords which are termed nerves, some of wiich 

 nerves end in the muscles, while others end in the organs of sen- 

 sation. That bare and bald statement of the fundamental com- 

 position of the nervous system will be enough for our present 

 purpose. 



The first proposition culled from the works of Descartes 

 which I have to lay before you, is one which will sound very 

 familiar. It is the view, which he was the first, so far as I know, 

 to state, not only definitely, but upon sufficient grounds, that the 

 brain is the organ of sensation, of thought, and of emotion — using 

 the word " organ " in this sense, that certain changes whi^h take 

 place in the matter of the brain are the essential antecedents of 

 those states of consciousness which we term sensation, thought, 

 and emotion. Nowadays that is part of popular and familiar 

 knowledge. If your friend disagiees with your opinion, runs 

 amuck against any of your pet prejudices, you «ay, "Ah ! 

 poor fellow, he is a little touched here;" by which you mean 

 that his brain is not doing its business properly, and, therefore, 

 that he is not thinking properly. But in Descartes' time, and I 

 may say for 1 50 years afterwards, the best physiologists had not 

 reached that point. It remained down to the time of Bichat a 

 question whether the passions were or were not located in the 

 abdominal viscera. This, therefore, was a very great step. It 

 is a statement which Descartes makes from the beginning, and 

 from which he never swerves. In the second place, Descartes 

 lays down the proposition that all the movements of animal 

 bodies are effected by the change of form of a certain part of the 

 matter of their bodies, to which he applies the general term of 

 muscle, ^'ou must be aware of this in reading Descartes ; you 

 must use the terms in the sense in which he used them, or you 

 will not understand him. That is a proposition which is now 

 placed beyond all doubt whatever. If I move my arm, that 

 movement is due to the change of this mass of flesh in front 

 called the biceps muscle : it is shortened and it becomes thicker. 

 If I move any of my limbs the reason is the same. As I now 

 speak to you, the different tones of my voice are due to the ex- 

 quisitely accurate adjustment of the contractions of a multitude 

 of such portions of flesh ; and there is no considerable and visible 

 movement of the animal body which is not, as Descartes says, 

 resolvable into these changes in the form of matter termed 

 muscle. But Descartes went further, and he stated that in the 

 normal and ordinary condition of things, these changes in th- 

 form of muscle in the living body only occur under certain con- 

 ditions ; and the essential condition of the change is, sa/s 

 Descaites, the motion of the matter contained within the nerves, 

 which go from the central apparatus to the muscle. Descartes 

 gave this moving material a particular name — the animal spirits. 

 Nowadays we should not talk of the existence of animal spirit?, 

 but we should say that a molecular change takes place in the 

 nerve, and that that molecular change is propagated with a 

 certain velocity, from the central apparatus to the muscle. 

 Nevertheless, the modification of the idea is not greater Ihan 

 that which lias taken place in our view of electricity, in our 

 change of conception of it as a fluid to our conception of it as a 

 condition of propagated molecular change. Modern physiology 

 has measured the rate of the change to which I have referred ; it 

 has thrown marvellous light upon its nature ; it has increased 

 our knowledge of its characters, but the fundamental conception 



