322 



Bacteria in Relation to Country Life 



solid excreta, the formation of ammonia occurred even 

 more rapidly, since all but five parts of the nitrogen 

 were converted into ammonia at the end of four days. 



It has been found that liquid excreta undergoes am- 

 moniacal fermentation more readily when the material 

 is more concentrated. This fact partly explains the 

 greater readiness of horse manure, as compared with 

 cow manure, to undergo this change. 



The transformation of urea and of hippuric acid into 

 ammonium carbonate is due to a number of bacterial 



Fig. 58. Urea bacteria. — 1. Urobacillus miguelii; X 9,000. Urobacillus leubii; 

 X 9,000. Planosareina ureas; X 9,000. (After Beyerinck.) 



species known as uro-bacteria. These may include rod- 

 shaped forms (uro-bacilli) and spherical forms (uro- 

 cocci). Uro-bacteria occur universally in nature and 

 may be readily isolated from soil, water, manure and air. 

 Ammonium carbonate is a volatile substance and easily 

 passes out of the manure and is lost. The danger of 

 loss is greatest in the summer months for the two-fold 

 reason that the bacteria work more rapidly at the higher 

 temperatures, and, also, because liquids evaporate 

 more rapidly under such conditions. 



