GERMS IN RELATION TO MILK 19 



Then, if the milk is immediately cooled to 40 F. and retained 

 at this temperature, the number of germs will lessen until it is 

 thirty-six hours old. 



The presence of many thousand germs to the cubic centimeter 

 in milk freshly withdrawn indicates filthiness of the cow, milker 

 or surroundings. This is especially so if the germs are of the putre- 

 factive or liquefying type (see p. 23). 



The existence of a great variety of germs in milk several hours 

 old signifies contamination of the milk with filth also, because in 

 clean milk only one kind of germs (lactic acid bacilli) are found 

 very numerous after many hours. 



While the mere fact that milk contains a vast number of germs 

 is not a sure proof of its unwholesomeness — because the commonest 

 germs in milk are harmless and because milk may contain but a few 

 germs and these may be the cause of dangerous disease in man — 

 yet the estimation of the number of germs in milk is to-day the 

 best method we possess for determining its purity. 



Ordinary market milk contains as many germs as sewage, and 

 unusually dirty milk contains more germs than sewage was ever 

 known to hold. This is, however, not at all a fair comparison, for 

 while sewage is likely to contain all sorts of germs of disease, the 

 germs in dirty milk are mostly not disease-germs. 



We may consider the influence of germs in milk under two- 

 heads: 1. The effect of germs on milk and its products. 2. The 

 influence of germs in milk on the consumer. 



I. The Effects of Germs on Milk and Its Products. — All 

 fermentation and putrefaction or rotting, anywhere and of anything, 

 are usually due to germs. The changes wrought in substances by 

 the " ferments " or chemical bodies — either produced by germs in 

 milk or secreted in milk— and by the ferments in the digestive juices 

 of animals, must also be included under the head of fermentation. 



Germs are the great disintegrating agencies in the world; 



