100 ORGANISM AND ENVIRONMENT 



seem to pass through an organism are constantly being 

 replaced. Nor is it mere form : for the flowing mate- 

 rial is intensely specific. Structure, composition and 

 activity are inseparably blended together in life, and 

 no phenomenon in the inorganic world seems to us to 

 be similar to the phenomenon of life. The funda- 

 mental facts with regard to life do not fit into the 

 conceptions by means of which we at present interpret 

 inorganic phenomena. Life is something which the 

 biologist as such must treat as a primary reality, and 

 no mere artifact. It is with life, and not merely with 

 physics or chemistry, or bio-physics or bio-chemistry, 

 that these lectures have dealt. From the outset of my 

 own scientific work I have been guided by the concep- 

 tion that it is with life, and not with what physics and 

 chemistry are at present capable of interpreting, that 

 physiology deals; and this conception has grown 

 clearer in my mind as a scientific working hypothesis 

 with advancing experience as a physiological worker. 

 What aims does this conception carry with it for 

 physiological investigation? The ground hypothesis 

 or conception is that each detail of organic structure, 

 composition, and activity is a manifestation or expres- 

 sion of the life of the organism regarded as a separate 

 and persistent whole. We have therefore to make 

 use of this hypothesis as a tool for investigation, just 

 as the physicist uses the conceptions of mass and 

 energy, or the chemist the atomic theory. We assume, 

 therefore, that it will be found on sufficient investiga- 

 tion that the scattered observations of living organisms 

 with which preliminary sensory observations supply 



