THE CAUSATION OF DISEASE. 309 



be separated from it. The term nutrition would more particu- 

 larly refer to the building-up, as distinguished from the 

 breaking-down, of the cell, to construction as against destruc- 

 tion (the latter constituting ' function '), but each process 

 would be essentially bound up with the vitality of the cells. 

 According to the later view, the muscle- cell elaborates muscle- 

 dynamite or inogen, the gland-cells elaborate zymogens, and 

 both are independent of and distinct from the actual fabric of 

 muscle or gland-cells. 



Which of these views is correct, or if either, I cannot tell ; 

 but this much may be said, that it is certainly convenient to 

 separate the nutrition or vital process of the cell from its 

 function, using the latter term as indicated. We can then 

 explain functional errors by imperfect nutrition of cells, without 

 presupposing any actual structural change, for, if the nutritive 

 processes of the cell fabric do not go on properly, the latter 

 will not be able to perforin its functions properly. I confess, 

 however, that I am not at all certain that we are justified in 

 making this distinction between nutrition and function, except 

 for purposes of convenience. And I have somewhat enlarged 

 upon the subject in order that the reader may henceforth 

 attach some definite meaning to the word function, as used in 

 the physiological sense, for I have nowhere been able to find 

 any intelligible definition of it. 



It may be asked: What is the meaning of "function" as 

 applied to a unicellular organism ? It seems to me that it here 

 simply refers to the vital processes of the organism. But in 

 a multicellular organism some one cell-capacity is exceedingly 

 developed, or there is an evolution of some new property which 

 is not actually necessary to the life of the cell, but serves some 

 purpose in the general economy of the organism, and it is 

 convenient to speak of this as the function of the cell. 



Viewed thus from the point of view of evolution, it is, 

 in a manner of speaking, impossible to separate such special 

 property from the vital process of the cell, for it has become 

 through long practice part and parcel of cell vitality — so much 

 so that if the cell were not to exercise its "function," atrophy 

 or degeneration would ensue. It is very probable, for instance, 

 that if the liver- cells ceased to secrete bile, they would 



Y 



