TEANSACTIONS OF SECTION D. DEPT. ANATOMY AND PHYSIOLOGY. 713- 



should be channels of information passing inwards, as that there should be channels 

 of influence passing outwards. Now what is the nature of these channels of infor- 

 mation i^ Experiment has taught us not merely with reference to the regulation 

 of the circulation, but with reference to all other automatic mechanisms, that they 

 are as various in their adaptation as the outgoing channels of influence. Thus the 

 vascular centre in the medulla oblongata is so cognisant of the chemical condition 

 of the blood which flows thi'ough it, that if too much carbonic acid gas is contained 

 in it, the centre acts on information of the fact, so as to increase the velocity of the 

 blood-stream, and so promote the arterial! sation of the blood. Still more strikingly 

 is this adaptation seen in the arrangement by which the balance of pressure and 

 resistance in the bloodvessels is regulated. The heart, that wonderful muscular 

 machine by which the circulation is maintained, is connected with the centre, as 

 if by two telegraph wires — one of which is a channel of influence, the other of 

 information. By the latter, the engineer who has charge of that machine sends 

 information to headquarters whenever the strain on his machine is excessive, 

 the certain response to which is relaxation of the arteries and diminution of 

 pressure. By the former, he is enabled to adapt its rate of working to the work it 

 has to do. 



• \^^ ^^' ^''^y^^' instead of cutting ofl' the head of his frog, had removed only 

 its brain — i.e. the organ of thought and consciousness — he would have been more 

 astonished than he actually was at the result ; for a frog so conditioned exhibits as 

 regards its bodily movements as perfect adaptedness as a normal frog. But very 

 little careful observation is suflBcient to show the difference. Being incapable of 

 the simplest mental acts, this true animal automaton has no notion of requiring 

 food or of seeking it, has no motive for moving from the place it happens to 

 occupy, emits no utterance of pleasure or distress. Its life-processes continue so 

 long as material remains, and are regulated mechanically. 



■'-° "'^"^'stand this all that is necessaiy is to extend the considerations which 

 have been suggested to us in our very cursory study of the nervous mechanism 

 by which the working of the heart and of arteries is governed, to those of loco- 

 motion and voice. Both of these we know, on experimental evidence similar to 

 that which enables us to localise the vascular centre, to be regulated by a centre 

 of the same kind. If the behaviour of the brainless frog is so natural "that even 

 the careful and intelligent observer finds it difficult to attribute it to anything less 

 than intelhgence, let us ask ourselves whether the chief reason of the difficulty- 

 does not he in this, that the motions in question are habitually performed intelli- 

 gently and consciously. Kegarded as mere mechanisms, those of locomotion are no 

 doubt more complicated than those of respiration or circulation, but the diflerence is 

 one ot degree, not of kind. And if the respiratory movements are so controlled and 

 regulated by the automatic centre which governs them, that they adapt themselves 

 pertectly to the varying requirements of the organism, there is no reason why we 

 should hesitate in attributing to the centres which preside over locomotion powers 

 which are somewhat more extended. 



But perhaps the question has already presented itself to your minds. What does 

 vi V V"?^*"-"" ^*^™ittiJig that we are able to prove (1) that in the animal 

 body, Troduct is always proportional to Process, and (2), as I have endeavoured 

 to show you in the second part of my discourse, that Descartes' dream of animal 

 automatism has been realised, what have we learnt thereby ? Is it true that the 

 work of the last generation is worth more than that of preceding ones ? 



It 1 only desired to convince you that during the last half-century there has 

 been a greater accession of knowledge about the function of the living organism 

 than during the previous one, I might arrange here in a small heap at one end 

 ot the table the physiological works of the Hunters, Spallanzani, Fontana, 

 Ihomas Young, Benjamin Brodie, Charles Bell, and others, and then proceeding to 

 cover the rest of it with the records of original research on physiological subjects 

 since 1831, I should find that, even if I included only genuine work, I should 

 bave to heap my table up to the ceiling. But I apprehend this would not give us a 

 true answer to our question. Although etymologically, Science and Knowledge 

 mean the same thing, their real meaning is different. By science we mean, first 



