THE APPLICATION OF PHYSICAL 

 METHODS TO PHYSIOLOGY 



By a. V. HILL. Sc.D., F.R.S. 



The University, Manchester 



Recent work on the nature of the atom has obliterated the 

 dividing hne between physics and chemistry : for practical 

 purposes the twin sciences will continue to be housed in separate 

 buildings, and discussed in separate text-books, but, as regards 

 the ultimate reality behind them, they rest unquestionably 

 upon the same foundations. In the following pages, therefore, 

 the word " physical " will be held to imply all those methods of 

 observation and reasoning which are common to the exact 

 sciences. On the biological side the trend of botany and 

 zoology towards the study of function, as well as form, the 

 growth of pathology as a laboratory science, and the formal 

 recognition of experimental medicine, have tended similarly 

 to break down the barriers between these sciences and physio- 

 logy : in the following pages, therefore, we shall use " physio- 

 logy " to denote the study of all the normal processes of life, 

 of the phenomena attending and of the mechanisms underlying 

 them, and of the co-ordination of those mechanisms. 



The word "mechanism " will at once evoke the echoes of a 

 controversy. It is believed by some that the processes of the 

 living creature are unlike those of the non-living world, in kind 

 not merely in degree, and that the use of the word " mechanism " 

 as descriptive of them is a false metaphor involving an un- 

 justifiable assumption. It is believed by others that, with the 

 progress of knowledge, the living creature will be proved to be 

 nothing but a complex system of co-ordinated mechanisms, 

 working according to the exact laws governing the exacter 

 sciences. The dispute between " vitalism " and " mechanism " 

 is one where no conclusion can be reached, but it serves, and 

 has served, a useful purpose in calling attention to the very 

 fundamental nature of the problems with which physiology 

 has to deal, and in showing the necessity to a physiologist of a 

 due acquaintance with the other sciences. The living creature 

 lives in a physical universe, bounded by physical barriers, dis- 



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