22 Manual of Veterinary 3Iicrobiology . 



A certain number of germs accommodate themselves 



equally well to both these ways of life; in the air 



they are aerobic, in its absence they become anaerobic. 



Tliis double faculty has been expressed by the term 



a'ero-anaerobic. 



III. Nutrition. 



1. Absorption and assimilation. — Absorption of food 

 takes place by osmosis. A part of the principles ab- 

 sorbed is utilized for the elaboration of plastic mate- 

 rial ; another part behaves as a respiratory food. The 

 formation of plastic material must be considerable 

 when we take into account the excessively rapid mul- 

 tiplication of micro-germs. 



The respiratory foods serve especially for the pro- 

 duction of the diilerent forms of work performed by 

 the elements, and which are represented by the phe- 

 nomena of assimilation, growth, locomotion, heat, 

 sometimes light (phosphorescence of meat and fish). 



Their intimate nutrition is little known. Chemi- 

 cally, the point of departure of the nutritive action is 

 quite dift'erent according to the case. Some require 

 albuminoids, whilst others draw their nitrogen from 

 azotized products with molecules of much less com- 

 plexity: leucin, tyrosin, xanthin, etc.; others again 

 borrow it from trimethylamin and from ammoniacal 

 salts. The same variety is observed in the case of 

 non-nitroffenous foods. 



This peculiarity accounts for the successive appear- 

 ance of different bacteria in an organic medium aban- 

 doned to the external air. As this medium becomes 

 more and more exhausted those species of germs suc- 

 cessively appear whose lesser requirements permit of 



