AMMONIACAL FERMENTATION OF URINE 219 



saccharose. Possibly the urease may diffuse from dead 

 cells, but it is most active as an intracellular enzyme of 

 the living bacteria. 



Comparatively little is known of the bacterial decom- 

 position of uric and hippuric acids. The nitrogen in 

 both appears to become changed into ammonium com- 

 pounds, but the stages of the process and the organisms 

 connected in it are very imperfectly known. In some 

 experiments carried out by F. and L. Sestini, a solution 

 of uric acid infected with decomposing urine and exposed 

 to the air was changed into ammonium bicarbonate and 

 carbon dioxide, and Gerard showed later that some 

 organisms hydrolyse the compound into urea and tar- 

 tronic acid, the former being acted upon later by the 

 uro-bacteria and changed into ammonium carbonate. 



Hippuric acid can be converted by acids and alkalis into 

 its constituents benzoic acid and glycocoll (amino-acetic 

 acid), and Van Tieghem states that the same change can 

 be induced by Urococcus urea. Burri considers that 

 calcium hippurate is fermented by certain bacteria with 

 the production of ammonium carbonate, and Schellmann 

 isolated a number of organisms from sewage and soil 

 which broke down hippuric acid and glycocoll to com- 

 pounds of ammonia, but not much is known of their 

 morphology or relationship. 



Micrococcus ureae. Cohn (M. Van Tieghemi, Miq.) is one of 

 the most prevalent of the urea bacteria in the air, water, soil, and 

 decomposing urine. It is a small coccus, .8 to 1.5 mm. in dia- 

 meter, met with usually singly or in pairs and tetrads, never in 

 chains. It does not form spores. Unlike most of the allied 

 uro-bacteria, it grows on ordinary nutrient media containing no 

 urea. 



Gelatine. The surface colonies on gelatine are non-liquefying, 



