IMPORTANT FOODSTUFFS, IMPORTANT TISSUES 117 



margarine, a butter substitute made largely from beef fat also 

 has been discussed in^uie chapter on fats. 



Cheese. When the caseinogen of milk is clotted by rennin 

 it separates out as a solid curd, which carries with it much of 

 the milk fat. This curd is cheese. Cheese is a very nutritious 

 foodstuff. Different kinds of cheese vary greatly in composi- 

 tion and food value. Average American cheese contains about 

 29% protein, 36% fat, traces of carbohydrate, 3.5% ash and 

 32% water. 



Meats. Meats are important food substances, for they fur- 

 nish large amounts of proteins, which are essential constitu- 

 ents of the diet. Meats contain a variety of proteins, but the 

 chief protein of dead muscle is myosin. Albumin, globulins 

 other than myosin, albuminoids, glycoproteins, nucleoproteins, 

 hemoglobin derivatives, and lecithoproteins all are constitu- 

 ents of meat, but in digestion all of these substances are broken 

 up into their constituent amino acids, the form in which pro- 

 tein food reaches the cells of the tissues. Meat also contains 

 fats, and small amounts of the carbohydrate glycogen or the 

 sugar derived from it. Most meats, with the exception of bacon 

 or very fat meats contain from 10 to 20% protein. Fat ranges 

 from a few per cent up to 60% in fat bacon. Ash ranges from 

 about 1% to 4 or 5%, water from about 7 or 8% to 68 or 70%. 



Eggs. Eggs are a very important article of diet. In the 

 development of the young of birds they furnish the material 

 out of which the tissues of the chick are built up. Eggs con- 

 tain (without the shell) about 12% protein, 11% fat, 0.5% 

 carbohydrate, 1% ash, and 75% water. Most of the fat is in 

 the yolk. About % of the protein is in the white and 

 % in the yolk. About 90% of the total protein of the white is 

 albumin. About 6i/ 2 % is globulin. Vitellin is the chief yolk 

 protein. All of these substances have been considered under 

 their respective groups. The yolk contains fat and also con- 

 siderable quantities of lecithin and cholesterol. 



Veg-etables. Vegetables contain very high amounts of water 

 and thus are low in fuel value. Some vegetables such as peas, 



