66 Dairy Bacteriology. 



tributed. According to Conn ' they are not very abun- 

 dant in perfectly fresh milk, but because of their ability to 

 thrive so luxuriantly in this liquid, they grow with great 

 rapidity, and therefore after a few hours milk always con- 

 tains them in abundance. 



It is a wide-spread belief that thunder storms cause milk 

 to sour prematurely, but this idea has no scientific founda- 

 tion. Experiments 9 with the electric spark, ozone and 

 loud detonations show no effect on acid development, but 

 the atmospheric conditions usually incident to a thunder 

 storm are such as permit of a more rapid growth of organ- 

 isms. There is no reason to believe but that the phenom- 

 enon of souring is wholly related to the development of 

 bacteria. Sterile milks are never affected by the action of 

 electric storms. 



" Gassy " milks. A large number of bacteria possess 

 the property of fermenting sugars and producing gases of 

 various kinds as well as acids of a volatile or fixed char- 

 acter. The amount of acid formed is generally consider- 

 ably less than that produced by the normal lactic species. 

 Among the gases formed, H and C0 2 are most common, 

 although N and CH 4 (methane) are sometimes produced. 

 In connection with these gases, there are also other de- 

 composition products of a more or less volatile nature that 

 frequently impart to the milk taints of an undesirable 

 character. 



While these " gassy " defects can often be recognized in 

 the milk itself, they are much more apt to cause trouble 

 in the manufacture of cheese (see Fig. 16), where, in severe 

 cases, curds may " float" or be "pin holey."* There are 



1 Conn, Agricultural Bacteriology, p. 191. 

 Treadwell, Science, 1804, 17: 178. 



Freudenreich, Landw. Jahr. cL Schweiz, 1890, p. 17; Russell, 12 Eept Wte. 

 Ezpt. Stat., 1895, p. 189. 



