CHAPTER IV. 



The Environment — The Environment of Unicellular Organisms — The Internal- 

 - Cell-Environment of Multicellular Organisms — The Primary Mai-Environ- 

 ment—The Secondary Mai-Environment— Remarks on the Nomenclature 

 of Disease. 



This and the following chapter will be devoted to the con- 

 sideration of that great factor in the vital process which we 

 may denominate " The Environment." The Environment, 

 or to use a convenient symbol, the " E " of multicellular 

 organisms, falls under a twofold division : into («), internal- 

 cell-E, and (b) external-body-E. The latter has to be divided 

 into organic and inorganic E, and further into mental and 

 physical E. 



A fit E, be it carefully noted, implies certain positive con- 

 ditions, and also certain negative ones. It requires, to wit, as 

 positive conditions, particular kinds of food, water, salts, oxygen, 

 and a particular temperature ; negatively, it requires the 

 absence of certain nocuous substances, notably, many products 

 of cell-action. Here let me remark that the term " material 

 conditions " embraces this absence of certain conditions as well 

 as the presence of others ; for if, to these positive conditions 

 Nvhich are necessary to life, others be added, the material con- 

 ditions will obviously not be the same. When, therefore, I 

 speak of " certain material conditions of E necessary to 

 healthful life," I obviously exclude such as are injurious or 

 fatal to it, and I take no account whatever of that large range 

 of indifferent conditions which do not affect it one way or the 

 other — for better or for worse. 



The influence of E upon cell-action is best studied in 

 unicellular organisms. We may instance the yeast plant 

 among numberless possible examples. This organism mul- 

 tiplies far more rapidly in some fluids than in others, but its 



c 



