318 STUDIKS IN ADVANCED PHYSIOLOGY. 



make an analysis of these mixtures and to determine the 

 amounts of each one of the classes just mentioned. The 

 accompanying table, modified slightly from Herman, shows 

 in a very striking way the composition of most of the com- 

 moner articles of food. By reference to it it will be seen 

 that the animal foods, such as the meats, contain very little 

 of carbohydrates, but relatively much of proteids and fat. 

 Of course the percentage of fat will vary within wide lim- 

 its, and will depend largely upon the condition of the ani- 

 mal examined. The leaner the animal, evidently the less 

 proportion of fat and the relatively larger proportion of pro- 

 teid. On the other hand, meat in which there is a good 

 deal of fat might finally have the fat in excess of the pro- 

 teid, a condition for instance found in ordinary breakfast 

 bacon. For this reason the animal foods, that is the meats, 

 have always been looked i:pon as the chief sources of the 

 nitrogenous foods, and as nitrogenous foods can not be dis- 

 pensed with in the diet, these foods have become popularly 

 viewed as almost if not wholly indispensable. 



On the other hand, the vegetable foods are quite sharply 

 distinguished by their relatively large amount of carbohy- 

 drates and rather small amounts of proteids and fats. Thus 

 the food value of the potato consists almost wholly of the 

 starch which it contains. Rice is nearly all starch. Even 

 in corn the starch is the largest ingredient, although in it 

 there are not inconsiderable quantities of proteid. In 

 wheat, in which the proteid gluten forms quite an integral 

 part of its composition, the carbohydrates occur in large 

 proportion. A rather remarkable exception of what has just 

 been stated occurs in the composition of peas, beans, and 

 other leguminous foods. In these the percentage of proteid 

 actually exceeds that found in meats. This explains why 

 these vegetables have commonly accredited to them such a 

 high nutritive value, and why sometimes in cases of mili- 

 tary operations when it is difficult to transport meats, beans 

 have been found a satisfactory substitute. 



