THE DEEPENING OF PHYSIOLOGY. 319 



of the living body, and we can also trace some of the 

 steps by which the waste products of activity are 

 got rid of. Our position may be compared to that 

 of visitors to the manufactory of some complex prod- 

 uct: they see the raw materials coming in, they are 

 allowed to follow the preliminary steps in their 

 transformation; they see the final products passing 

 out, and they are allowed to witness the process of 

 " finishing " them ; they see the rubbish that is cast 

 away and are shown how some of the waste-products 

 are re-utilised; but what they do not see is the gist 

 of the Avhole business — the affairs of ^^ the secret 

 room " — where the essential transformations are kept 

 secret. 



Metabolism. — All theory apart, it is a fact of ob- 

 servation that there is in the living body a twofold 

 process — of waste and of repair, of disruption and 

 construction, of disassimilation and assimilation. 



*' One of the first to make this general idea more 

 precise was De Blainville, who described vitality ' as a 

 twofold internal movement of composition and decom- 

 position.' At a later date, Claude Bernard, who may 

 be called the pioneer of the * protoplasmic movement,' 

 distinguished * disassimilating combustion and assimi- 

 lating synthesis.' Of recent years various researches 

 and speculations, especially those of Tiering and of 

 Gaskell, have led to yet more precise statements in re- 

 gard to metabolism." * 



Prof. Hering says : " Assimilation and disassimi- 

 lation must be conceived as two closely interwoven 

 processes, which constitute the metabolism (unknown 

 to us in its intrinsic nature) of the living subtance, 

 and are active in its smallest particles, — since living 

 * Thomson, Science of Life, p. 114. 



