The Lactic Acid Germ. 73 



tion of poisonous products. These products are the 

 causes of the serious or even fatal results that fol- 

 low the consumption of milk, cheese, ice-cream, or 

 other products containing them. They are collect- 

 ively known as ptomaines. To one in particular, 

 that has frequently been found in cheese, the name 

 tyrotoxicon (cheese -poison) has been given. They 

 have been studied by Vaughn* and others, but 

 their origin is still obscure. The germs producing 

 these poisonous products are of comparatively in- 

 frequent occurrence. 



In general, the various classes of fermentations do 

 not readily take place at the same time. The active 

 growth and development of one germ acts more or 

 less as a retarding force upon the growth and de- 

 velopment of other germs. 



Lactic fermentations. — Under this group we include 

 all of those germs which, living and growing in 

 milk, feed upon the sugar, causing it to change to 

 lactic acid. It was formerly supposed that the forma- 

 tion of lactic acid in the milk was entirely due to the 

 action of a single germ, described by Hueppe, and 

 called Bacillus acidi-lactici, or the lactic acid germ. 

 It is now known that there are at least twenty different 

 germs that may produce lactic acid, and in all prob- 

 ability there are many more. The lactic acid germs 

 are the most common and most numerous germs 

 found in milk, and ordinarily the lactic fermentations 

 are the first to take place. They begin their opera- 



* Vaughn-Novy. Ptomaines and Leucomaines, Philadelphia, 1896. 



