BACTERIA COMMONLY FOUND IN COWS' MILK. lOl 



tious bacteria, as the Mastitis bacterium and some color- 

 producing bacteria, as the Bacillus prodigiosus, belong here. 

 The latter has not, to my knowledge, been found ill our 

 country.* 



1. Butyric Fermentation. The form of the many 

 butyric-acid bacteria which I have met with in this coun- 

 try has in the main proved similar to the one first isolated 

 and described by Hueppe. It is aerobic, and produces a 

 slight coagulation of the casein, which, however, later on 

 is peptonized. It may therefore also be referred to one of 

 the following groups. If sterilized milk be inoculated 

 with such butyric-acid bacilli, a clear liquid layer of a gray- 

 ish color will be found after keeping the cultures for a 

 couple of days at about 86 F. (30 C.). Under this layer 

 a lumpy casein coagulum is found, which sinks deeper 

 as the clear liquid increases. The coagulum gradually 

 disappears, and after some time will be entirely pepton- 

 ized. Milk changed in this way has a very bitter taste. 



Ic. Bacteria Producing Volatile Acids. Among the 

 bacteria producing volatile acids in the milk may be men- 

 tioned first the tfdwo-bacteria forms, which are rather fre- 

 quent in milk. They all appear with a translucent, sack- 

 formed cover, in which the fine, long, immovable bacteria 

 are entirely wrapped up, and in which the division of the 

 bacteria seems to take place. Some hours after the ster- 

 ilized milk has been inoculated with such bacteria the sam- 

 ple will be changed both in appearance and consistency. 

 It assumes a brown to grayish color and becomes rather 

 viscous. No appreciable coagulation will be found. Grad- 

 ually the milk will be changed to a translucent, grayish- 



* The same is true in case of America (Russell). W. 



