864 TRANSACTlOJfS Oi SECTIoN 1. 



Section I.— PHYSIOLOGY. 

 President of the Section. — J. S. Haldane, M.D., F.R.S. 



TlJVnSDAY, SEPTEMBER 3. 



The President delivered tlie following Address : — 



The Jielation of Physiology to Physics and Chemistry, 



In choosing to address you on the relation of Physiology to PhysicS and 

 Chemistry, I am aware that I have selected a sahject which has already been 

 ti-eated from this Chair by more than one distinguished predecessor. My excuse 

 for returning to it again is that it not only possesses deep scientific interest for 

 us all, but that a great deal remains to be said about it. 



The majority of physiologists in recent times haVe expressed more or less 

 clearly the opinion that Physiology is the application to living organisms of the 

 methods and modes of explanation of Physics and Chemistry. It is, in short, 

 Physics and Chemistry applied to the activities of living organisms; so that 

 the only explanations aimed at in Physiology are, or ought to be, physical and 

 chemical explanations. A minority, wbich is at present a growing one, I think, 

 have either definitely dissented from this view, or have remained unconvinced of 

 its truth. As one of this minority I should like to place before you as shortly 

 as possible what seem to me tO be the main reasons of our dissent. Let me add 

 that I have carefully i)ondered over these reasons during many years of active 

 physiological work. 



When we look back on the history of Physiology it seems perfectly evident 

 that physiological progress has been dependent on the progress of Physics and 

 Chemistry. On this point there is no room for doubt. To take only one 

 example, where should we be in the investigation of animal metabolism but Jor 

 the ideas and experimental methods furnished to us by Pliysics and Chemistry ? 

 We should know next to nothing about respiration, animal heat, nutrition, or 

 muscular and other work, Physiology depends at every turn on Physics and 

 Chemistry, and its future progress will certainly be equally dependent on 

 advances in physical and chemical knowledge. This consideration has, I imagine, 

 weighed very heavily in the minds of those physiologists who have concluded 

 that Physiology is nothing but applied Physics and Chemistry. A further fact 

 which weighs equally heavily is that in spite of diligent search no fact contra- 

 dicting the fundamental laws of conservation of matter and energy has been 

 discovered in connection with living organisms. 



AVlien, however, we ask what progress has been made towards the physico- 

 chemical explanation of physiological processes, we at once enter upon contro- 

 versy. We may point to advances in some directions, but they are accom- 

 panied by the appearance of unforeseen diificulties in other directions. Again, 

 to take animal metabolism as a typical instance, the investigations of the last 



