78 FOOD MATERIALS 



ness. It becomes butter when the thin membranes which 

 cover the fat drops are broken open by churning. 



After the cream and cheese have been removed from 

 milk, the sugar remains in solution and can be ob- 

 tained by evaporating the water. Milk sugar is a val- 

 uable article of food and is used largely in the feeding 



FIG. 54. A portion of a drop of cow's milk highly magnified, showing the fat 

 globules. 



of infants. It helps to make cow's milk more like 

 human milk and so makes it better adapted to their 

 digestion. 



Contamination of milk. Since milk is so valuable a 

 food, it is most unfortunate that it is difficult both to 

 get and to keep it clean and fresh. In the cow itself, 

 on the hands of the milkmen, in the pails, cans and bot- 

 tles, may lurk millions of microbes, some of which are 

 not infrequently productive of disease. Only the milk 



