MICROBES, OR BACTERIA. 109 



those of the orifice of the urethra, can produce this 

 fermentation. Since the latter are always carried off 

 by the first discharge of urine, only the second por- 

 tions of the emitted liquid should be collected in 

 a perfectly clear vessel, which has been sterilized, 

 or, carefully freed from all atmospheric germs. The 

 vessel should then be put under a glass shade to 

 protect it from these germs, and if all proper pre- 

 cautions are taken, the urine will remain clear and 

 acid for an indefinite time without undergoing am- 

 moniacal fermentation. If afterwards a little plug 

 of amianthus, which has been previously sterilized 

 by heat, should be introduced by a small pair of 

 pincers into the urethra to a depth of two centi- 

 metres, and then dropped into this untransformed 

 urine, it will soon be transformed, and undergo am- 

 moniacal fermentation. But if the plug of amianthus 

 has been steeped in an antiseptic solution (diluted 

 carbolic acid) before being introduced into the urethra, 

 it will not produce this fermentation. 



VII. BUTYRIC FERMENTATION OF BUTTER, CHEESE, 

 AND MILK. 



Butyric fermentation follows lactic fermentation in 

 milk, butter, and cheese, and it is butyric acid which 

 gives to butter its rancid taste. This fermentation 

 also occurs in saccharine substances, and generally 

 in all proteid substances. 



