62 BACTERIOLOGY 



clear zone in which the deeply stained central mass lies. 

 Occasionally the central protoplasmic mass is surrounded 

 by an ill-defined slimy material that causes the individual 

 cells to adhere to one another in more or less compact masses 

 or pellicles (zooglea, Fig. 1). 



Chemical Composition of Bacteria. — ^The bodies of bacteria 

 consist of water, salts, and albuminous substances, with 

 smaller proportions of various extractives soluble in alcohol 

 or ether, such as triolein, tripalmitin, tristearin, lecithin, 

 and cholesterin. In many varieties substances giving the 

 reaction of starch have been found, while others give the 

 true reactions of cellulose {B. subtilis). Nuclein has not 



Fig. 1 



Zooglea of bacilli. 



been found in any of the bacteria, though the nuclein bases, 

 xanthin, guanin, adenin, have been found. 



The relative amounts of water in bacteria are influenced 

 to a large extent by the nature of the medium on which 

 they have been grown. In like manner the content in 

 albumin, extractive substances, and salts varies with the 

 conditions under which the bacteria have been cultivated. 

 E. Cramer^ has studied the chemical composition of bacteria 

 in great detail. As the result of his studies of microspira 

 comma, he found its composition to be as follows: water 



' Arohiv fiir Hygiene, Bd. xiii, xvi, xxii, and xxviii. 



