80 FOOD MATERIALS 



.as nearly at the temperature of ice as possible. In this 

 way, the development of microbes, which is exceedingly 

 Tapid in warm milk, 1 may be checked. 2 



Eggs. Eggs are another important food contributed 

 by animals. Every egg is a package of food especially 

 prepared for the nourishment of the young animal con- 

 tained within it, during its development. It is, therefore, 

 a complete food for an actively growing animal. It 

 consists of a transparent portion, the egg albumin, and 

 a yolk which contains a relatively large amount of fat 

 together with proteid and other substances. As a com- 

 plete food for man, it lacks carbohydrate material. 



Eggs are valuable as food whether eaten raw, slightly 

 cooked or thoroughly boiled. When heated, the white 

 coagulates into a firm hard mass, which when well 

 chewed is not indigestible. Fried eggs are least digesti- 

 ble because the white is made tough by the hot grease. 



Neither milk nor eggs are very economical foods except 

 in the country. The same amount of nutriment, al- 

 though not always in so pleasing or digestible a form, 



1 The development of microbes in milk at different temperatures 

 is about as follows: 



Temperature At end of 24 hrs. At end of 48 hre. 



60 180,000 28,000.000 



68 450,000 25,000,000,000 



86 1,400,000.000 



94 25,000,000,000 



Uelow 50, the development of microbes in milk is comparatively 

 slow. 



2 It was formerly a common practice to get rid of the microbes 

 in milk for infants by heating it to a boiling point (sterilisation). 

 In recent years, however, it has been found that to heat milk in 

 this way so changes its character that it lessens its value as food. 

 The best practice therefore seems to be to prevent the entrance 

 of microbes into the milk and their subsequent development, in 

 order that the milk may be as safe as possible in its raw state. 

 Still greater safety may be insured for infant feeding by heating 

 the milk to 150-160 F. for 15 minutes (Pasteurization), and 

 then putting it upon ice. Even pasteurization, however, does not 

 protect against the germs of tuberculosis. 



