142 PHYSIOLOGY OF THE BACTERIA. 



Ammoniacal Fermentation of Urine. When 

 urine is freely exposed to the air, we perceive at 

 the end of a short time that it has become strongly 

 ammoniacal. The urea is transformed into carbon- 

 ate of ammonia by the addition of water : 



CO(NH 2 ) 2 + H 2 = CO 2 + 2NH 3 . 



Miiller suspected that the deposit of altered 

 urine, of which Jacquemart had already recognized 

 the particular activity, was an organized ferment, 

 but this was only an induction drawn from the 

 analogy with beer yeast. Pasteur showed that 

 this sediment is formed of a mass of spherical 

 globules, united in chaplets, which he considers the 

 agent of ammoniacal fermentation. These glob- 

 ules are Micrococcus urece, Cohn, which we have 

 already described (page 75). 



This bacterium lives in the interior of the liquid, 

 and not on the surface like the Mycoderma aceti. 

 Acidity is an obstacle to its development ; alkalin- 

 ity, on the contrary, favors it within certain limits. 

 Van Tieghem has even seen the fermentation con- 

 tinue until the liquid contained thirteen per cent 

 of carbonate of ammonia. 



What is the mechanism of this fermentation ? 



M. Musculus has shown that we may obtain 

 from altered urine a soluble ferment upon adding 

 to it highly-concentrated alcohol : a precipitate is 

 formed, which may be filtered and dried. This 

 precipitate, not at all organized, transforms urea 

 into carbonate of ammonia. A temperature of 

 80 (176 Fah.) destroys it. This diastase appears, 



