CHEMICAL COMPOSITION OF BACTERIA. 51 



so thick as to be readily seen, while again it is discerni- 

 ble only by special methods of examination. In partic- 

 ular species it may, by appropriate methods, be seen as 

 a sharply defined capsule inclosing a 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 (zoogloea, Fig. 1). 



FIG. 1. 



Zoogloea of bacilli. 



CHEMICAL COMPOSITION OF BACTERIA. The bodies 

 of bacteria consist of water, salts, and albuminous sub- 

 stances, with smaller proportions of various extractive 

 substances 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 (I>. subtilis). Nuclein has not been found 

 in any of the bacteria, though the nuclei n bases, xan- 

 thin, guanin, adenin, have been found. 



The relative amounts of water in bacteria are influ- 

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

 which they have been grown. In like manner the con- 

 tent in albumin, extractive substances, and salts varies 

 with the conditions under which the bacteria have been 

 cultivated. E. Cramer 1 has studied the chemical com- 



1E. Cramer: Archiv. fiir Hygiene, lid. xiii., xvi., xxli., and xxviii. 



