CHAPTER III 



CHEMICAL STUDIES OF THE CONTENT OF MICROBIAL 



CELLS* 



Microorganisms have a widely variable chemical composition. 

 They differ so much in their requirements their habits, their food 

 needs, their moisture demands, their environmental atmosphere, and 

 their capacity for change that their great deviation from a constant 

 nature, as manifested by superficial expressions, perhaps, does not 

 awaken unexpected mental responses. They also undergo much 

 alteration in their compositional nature as well as in their structural 

 nature while passing stages in their individual developments. The 

 vegetative or growing forms do not seem to have the same composition 

 as the spore-forms or resting forms although it may be quite possible 

 that fundamentally the exact composition exists in both and only more 

 superficial substances are detectable; old cells differ from young cells 

 and capsulated forms from uncapsulated forms. Food influences 

 greatly the products found in protoplasm both quantitatively and 

 qualitatively. While such products which are referable to food may 

 not be strictly a part of what is contemplated in the composition of the 

 cell, yet it is difficult many times to make the distinction. Doubtless 

 most influencing agents whether external or internal have some power 

 over the substances now recognized in cellular composition. 



If, however, constancy in species is to be maintained, it is necessary 

 to assume that there is to be found in every species a constant group or 

 nucleus of chemical atoms or molecules whether existing independently 

 or acting in consort in forming congeries of molecular complexes, and 

 that substances fluctuating in their presence or in their amount must 

 be regarded as more incidental to the basic life-processes. Species, 

 therefore, even when undergoing all the recognized variations to which 

 it is subjected ageing, developmental stages, reproduction, environ- 

 mental factors as food, reaction, oxygen supply, temperature, and others 



* Prepared by Charles E. Marshall and Arao Itano.. 



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