CHEMICAL COMPOSITION OF BACTERIA. 51 



position of bacteria, quantitatively, by the studies of 

 Cramer, though so far only a few species have been 

 thoroughly investigated. The percentage of water 

 contained in bacteria grown on solid culture media, as 

 well as the amount of ash, depend largely on the 

 composition of the media. Thus the bacillus prodigio- 

 sus when grown on potato contains 21.5 per cent, of 

 dry residue and 2.7 per cent, of ash ; when cultivated 

 on turnips it contains 12.6 per cent, of dry residue and 

 1.3 per cent, of ash. Beside the concentration of the 

 culture, its temperature and age also influence the 

 amount of residue and ash produced. The residue 

 varies, moreover, in its composition in the same species 

 under the influence of the culture media employed. 

 Thus the Friedlander pneumonia bacillus grown on 

 nutrient agar containing peptone yields of residue : 



With 1 per cent. With 5 per cent. 



peptone. peptone. 



Nitrogenous matter . 71.7 per ct. 79.8 per ct. 

 Extractives . . . 10.3 " 11.3 " 



Ash .... 13.9 " 10.3 " 



With 1 per ct. peptone 



+ 5 per ct. glucose. 

 Nitrogenous matter .... 63.6 per ct. 



Extractives . . . . . .22.7 " 



Ash . 7.8 " 



It would thus appear that an additional quantity of 

 peptone in the culture media tends to increase the per- 

 centage of nitrogenous matter in the bacillus, while 

 the addition of glucose decreases it. 



The cholera spirillum shows still greater variations 

 in the residue when grown in soda bouillon containing 

 albumin than in Uschinsky's medium, which is free 

 from albumin. Thus Cramer found as an average 



