278 



Agricultural Chemistry. 



sugar. It is upon these chemical facts that the modification of 

 cow 's milk, by dilution and addition of lactose, rendering it suit- 

 able for infant feeding, is based. However, experience is teach- 

 ing that in most cases the whole milk of the cow, without dilution, 

 'can be safely used for infant feeding. There is a growing be- 

 lief, though, that it must not be too rich in fat. 



Preservation of milk. Normal milk as it occurs in the cow's 

 udder usually contains relatively few organisms; but in the 



Composition of Milks. 



operation of milking and during subsequent exposure to the air, 

 bacteria, molds and yeasts find admission. They may find their 

 way into the milk from the hands of the milker, the teats anc 

 hair of the cow, and often from the vessel in which the milk is 

 collected. The ordinary souring of milk is produced by various 

 species of bacteria, which during their growth convert the milk- 

 sugar into lactic acid. This formation of acid induces the curd- 

 ling of the milk. This generally occurs when the amount of acid 

 reaches about 0.7 per cent. Curdling is produced by less acid 

 if the milk is heated. 



Other organisms, and often of a more dangerous character 



