30 CHEMICAL COMPOSITION. 



carbohydrate, C 6 H 10 O 5 , "dextran"; Kramer has obtained 

 a similar substance from the capsules of the Bac. viscosus 

 sacchari. Up to this time, nuclei n has not been obtained 

 from bacteria in any quantity; on the contrary, of the nu- 

 clein bases, xanthin, guanin, adenin have been obtained 

 in considerable quantities. A number of bacteria con- 

 tain sulphur granules, which have arisen from sulphur- 

 etted hydrogen (Beggiatoa thiothrix). Others, still con- 

 sidered as belonging to the bacteria by many authors, 

 deposit oxid of iron in their capsules, obtaining it from 

 water containing iron (cladothrix, crenothrix). 



Regarding quantitative composition, the methodical 

 work of E. Cramer has added considerable light, though 

 up to the present exact statements are submitted regarding 

 only the B. prodigiosum, B. pneumoniae, and some related 

 organisms, and also a series of cultures of the Vibrio choleras. 

 Compare E. Cramer, A. H. xiii, 71; xvi, 151, and xxn, 

 p. 167. 



The water content of a culture grown on solid nutrient 

 media, as also the amount of ash, depend in a very large 

 measure upon the composition of the medium. 



For example, the B. prodigiosum contained, when grown upon po- 

 tato, 21.49% dry substance, 2.70% ash in the fresh substance; when 

 grown upon yellow turnip, 12.58% dry substance, 1.31% ash in the 

 fresh substance. Besides the concentration of the nutrient medium, 

 higher temperature and lessened age of the culture act to increase the dry 

 substance and the ash. 



Also the dry substance of bacteria varies in its compo- 

 sition under the influence of the nutrient medium. 



Thus, for example, the Bact. pneumoniae Fried, shows upon meat- 

 infusion agar containing 



1 # Peptone and 5 <f> 

 1 # Peptone. Grape-sugar. 



Albumin 71.7% 63.6% 



Ethereal and alcoholic extractives 10.3% 22.71 % 



Ash . . 13.94% 7.88% 



m 



Evident increase in the proportion of peptone in the 

 nutrient medium leads to an increase in the albumin iR 

 the bacteria, while increase of grape-sugar makes the body 

 substance poorer in albumin and increases the alcoholic 

 and ethereal extractives (Lyons; A. H. xxvni, 30). 



