828 president's address. 



a strictly logical continuation of that effort to account for the 

 phenomena of life on the lines of physical causation which the 

 introduction of the conception of natural selection seemed to 

 bring within our reach. In other words, its object is, like that 

 of every purely naturalistic theory, to explain away the teleological 

 phenomenon of adaptation which had appeared to the older biolo- 

 gists to be, prima facie, the cardinal characteristic of all organic 

 process. It aims at replacing the idea of purpose or final cause 

 by the purely physical idea of determination by efficient cause as 

 the ordinary and necessary procedure of all scientific interpreta- 

 tion. 



This mechanical tendency in the treatment of the relations of 

 the organism to the external world and to other organisms, in 

 space and time, is not its only expression in modern biological 

 thought. On the physiological side also, dealing with life as 

 manifested in the inner relations of the parts and organs of the 

 body to one another, the same spirit has been active. 



The vitalistic interpretations and theories which were current 

 earlier in the century have been subjected to a progressive 

 destructive criticism, and it has been claimed that the more 

 insight we get into the true character of living process, the more 

 clearly does it appear that their natural explanation must come 

 to us in terms of physics and chemistry if at all. And there are 

 abundant proofs that the application of physico-chemical ideas 

 and methods to the investigation of vital phenomena is able to 

 carry us further in the direction of an intelligible explanation of 

 living processes than could formerly have been dreamed of. 



Whatever may be the final explanation forced upon us of the 

 real nature of the operation of living activity in an animal 

 organism, it is beyond doubt that our acquaintance with the 

 manner of that operation has grown enormously along with the 

 assumption of its essential identity with inorganic process. 



Yet in spite of this there have been many indications during 

 the latter part of this century of a reaction away from mechanical 

 and back towards vitalistic interpretation. 



