GENERAL METABOLISM. 



659 



it would be dangerous to continue milk as the sole food for too long a 

 time. In the case of the human race, milk plays a more or less important 

 function as food during the whole period of growth and even for adults. 

 The utilization of the material in milk is somewhat greater on the part 

 of the infant than is the case with the adult, but even then it remains 

 very satisfactory. Cow's milk is utilized to good advantage by the human 

 offspring. 



One very important food for the growing organism, as well as for the 

 adult, is the egg. In the raw state, as well as when hard boiled, the egg is 

 equally well utilized. As far as we are concerned, the eggs of birds alone 

 come into consideration, and especially those of hens. 



In 100 grams of fresh eggs there are present : 73.7 grams water, 12.6 

 grams nitrogenous matter, 12.0 grams fat, 0.7 gram nitrogen-free extrac- 

 tive substances, and 1.07 grams of ash. The percentage composition of 

 the last-mentioned is as follows : * 



The greater part of the phosphorus contained in eggs (about 80 per cent) 

 is present in lecithin, nuclein, and other organic compounds. Only a 

 small part is found in the form of inorganic salts. 



Flesh foods form one of the most important articles of diet for adults. 

 The amount eaten varies with different nations and with different classes 

 of people. According to Ostertag 2 the consumption per head in different 

 localities is as follows: 



In China even less meat is eaten than in Italy. Similarly certain negro 

 races live almost entirely upon vegetables. The composition of meat as 



1 Konig: loc. cit. p. 576. 



2 R. Ostertag: Handbuch der Fleischbeschau, p. 4. Stuttgart, 1899. 



