168 Dairy Bacteriology. 



would be if it was caused by a single specific organism. 

 There are present in all milks a few bacterial forms that 

 are able to produce a varied series of fermentations in 

 which different gases may be given off. Among these 

 organisms are a large number of .the bacteria, although 

 yeasts and allied germs are often present in milk and are 

 likewise able in some cases to set up fermentative changes 

 of this sort. In these cases the milk-sugar is decom- 

 posed in such a way as to give off CO 2 and H, and in 

 some cases, alcohol. 



According to Guillebeau a close relation exists between 

 those germs that are able to produce an infectious inflam- 

 mation (mastitis) in the udder of the cow and some forms 

 capable of gas evolution. Several outbreaks of "gassy" 

 milk have been traced directly to animals suffering from 

 an acute inflammatory condition of the udder in which 

 it has been shown that the organisms producing this dis- 

 ease were the direct cause of the gas production in the 

 milk. 



Gas-producing bacteria are so numerous that they are 

 almost always present in any sample of milk, especially 

 if it is a little old. Bolley and the writer isolated six 

 different species from a single sample of summer milk. 

 Even in winter we have found them present in milk in 

 such numbers as to require special care in the manufac- 

 ture of cheese. Under normal conditions, where care is 

 taken in the handling of the milk, they are not usually 

 found in large numbers, and when thus numerically re- 

 stricted, are doubtless kept under subjection by the com- 

 petition of numerous other bacteria in the milk. 



These fermentations are very often observed in foreign 

 kinds of cheese, especially those that are made after the 

 sweet-curd process. Adametz 1 has collated data on the 



1 Adametz, Die Ursachen u. Erreg, d. abnorm. Reif. Vorg. b. 

 Kaese, p. 27. 



