BACTERIA IN FOODS 185 



the mid-milk. As a matter of fact, most of this large num- 

 ber belong to the lactic-acid fermentation group, and the 

 fore-milk rarely contains more than two or three species, and 

 still more rarely any disease-producing bacteria. Still, they 

 occur in such enormous numbers that their addition to the 

 ordinary milk very materially alters its quality. Bolley and 

 Hall, of North Dakota, report sixteen species of bacteria in 

 the fore-milk, twelve of which produced an acid reaction. 

 Dr. Veranus Moore, of the United States Department of 

 Agriculture, 1 concludes from a large mass of data that 

 freshly drawn fore-milk contains a variable but generally 

 enormous number of bacteria, but only several species, the 

 last milk containing, as compared with the fore-milk, very 

 few micro-organisms. The bacteria which become localised 

 in the milk-ducts, and which are necessarily carried into the 

 milk, are for the greater part rapidly acid-producing organ- 

 isms, i. e., they ferment milk-sugar, forming acids. They 

 do not produce gas. Still their presence renders it neces- 

 sary to " pasteurise " as soon as possible. Dr. Moore holds 

 that much of the intestinal trouble occurring in infants fed 

 with ordinarily " pasteurised " milk arises from acids pro- 

 duced by these bacteria between the drawing of the milk 

 and the pasteurisation. 



The Number of Bacteria in Milk. From all that has been 

 said respecting the sources of pollution and the favourable 

 nidus which milk affords for bacteria, it is not surprising 

 that a very large number of germs are almost always present 

 in milk. The quantitative estimation of milk appears more 

 alarming than the qualitative. It is true some diseases are 

 conveyed by bacteria in milk, but on the whole most of the 

 species are non-pathogenic. Nor need the numbers, though 

 serious, too greatly alarm us, for, as we shall see at a later 

 stage, disease is a complicated condition, and due to other 

 agencies and conditons than merely the bacteria, which may 



1 Bureau of Animal Industry Reports, 1895-1896. 



