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, 
VIL 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, 
