FOODS. 321 



animals will not develop normally in water from which all 

 calcium salts have been removed. 



Mixed Poods. These, as already pointed out, include 

 nearly all common articles of diet; they contain more than 

 one alimentary principle. Among them we find great differ- 

 ences; some being rich in proteids, others in starch, others in 

 fats, and so on. The formation of a scientific dietary depends 

 on a knowledge of these characteristics. The foods eaten by 

 man are, however, so varied that we cannot do more than 

 consider the most important. 



Flesh. This, whether derived from bird, beast, or fish, 

 consists essentially of the same things muscular fibres, 

 connective tissue and tendons, fats, blood-vessels, and nerves. 

 It contains several proteids, especially rnyosin; gelatin-yield- 

 ing matters in the white fibrous tissue; stearin, palmatin, 

 and olein as representatives of the fats; and a small amount of 

 carbohydrates in the form of glycogen and grape-sugar, or 

 some chemically allied substances. Flesh also contains much 

 water and a considerable number of salines, the most important 

 and abundant being potassium phosphate. Osmazome is a 

 crystalline nitrogenous body which gives much of its taste to 

 flesh; and small quantities of various similar substances 

 exist in different kinds of meat. There is also more or less 

 yellow elastic tissue in flesh ; it is indigestible and useless as 

 food. 



When meat is cooked its white fibrous tissue is turned 

 into gelatin, and the whole mass becomes thus softer and 

 more easily disintegrated by the teeth. When boiled some 

 of the proteid matters of the meat pass out into the broth, 

 and there in part coagulate and form the scum : this loss may 

 be prevented in great part by putting the raw meat at once 

 into boiling water which coagulates the surface albumen be- 

 fore it dissolves out, and this keeps in the rest, while the 

 subsequent cooking is continued slowly. In any case the 

 myosin, being insoluble in water, remains behind in the boiled 

 meat. In baking or roasting, all the solid parts of the flesh are 

 preserved and certain agreeably flavored bodies are produced, 

 as to the nature of which little is known. 



Eggs. These contain a large amount of egg albumen 

 and, in the yolk, another proteid, known as vitellin. Also 

 fats, and a substance known as lecithin, which is important 

 as containing a considerable quantity of phosphorus. Leci- 



