NITROGENIZED ALIMENTARY PRINCIPLES. 177 



developed in cooking; but the organic principle of all of them is musculine. Muscular 

 tissue is rendered much more digestible by cooking, a process which serves to disin- 

 tegrate, to a certain extent, the intermuscular areolar tissue and facilitates the action of 

 the digestive fluids. The savors developed in this process have a decidedly favorable 

 influence on the secretion of the gastric juice. It is doubtful whether pure musculine 

 would be capable of supporting life for a long period ; but the muscular tissue has been 

 shown by experiment to be sufficient for the purposes of nutrition, in the carnivora, and 

 it undoubtedly is in man. 



Of all kinds of muscular tissue, beef possesses the greatest nutritive power. Other 

 varieties of flesh, even that of birds, fishes, and animals in a wild state, do not present 

 an appreciable difference, as far as can be ascertained by chemical analysis ; but when 

 taken daily for a long time, they become distasteful, the appetite fails, and the system 

 seems to demand a change of diet. The flesh of carnivorous animals is rarely used as 

 food; and animals that feed upon animal as well as vegetable food, such as pigs or 

 ducks, acquire a disagreeable flavor when the diet is not strictly vegetable. 



Albumen. This is an alimentary principle hardly second in importance to musculine. 

 As an article of diet, it is chiefly found in the white of egg, where it exists in great 

 quantity and is combined with a variety of inorganic substances. Although an important 

 alimentary principle, it cannot meet all the nutritive requirements of the organism. 

 Numerous observations on the inferior animals have shown that pure albumen will not 

 sustain life. The egg of the fowl, however, containing, in addition to albumen, a large 

 quantity of inorganic matter, the fatty matter of the yolk, and other 'organic principles, 

 is a most nutritious article of food. The albuminoid matters constitute the great 

 nutritive nitrogenized principles of the blood and are the substances into which all the 

 principles of this class which exist in food are converted before they are applied to the 

 nutrition of the tissues. 



Gaseine. At a certain period of life, caseine constitutes essentially the sole nitrogenized 

 article of food. It is found only in milk, and it exists largely in the great variety of 

 cheeses, which are manufactured from milk. In addition to caseine, milk contains butter, 

 sugar, and a variety of inorganic principles. Milk is capable of supplying material for 

 the nourishment of all parts of the organism, caseine furnishing the nitrogenized prin- 

 ciple. In the form of cheese, caseine constitutes an important article of food. 



Fibrin. Fibrin is by no means so important an article of diet as those just considered, 

 and it very seldom forms any considerable part of our food The aame may be said of 

 some other principles of this class, such as globuline, which is the organic principle of the 

 blood-corpuscles, vitelline, a principle peculiar to the yolk of the egg, osteine and car- 

 tilagine. The last two substances are generally taken after they have undergone peculiar 

 modifications in cooking, when they are known by other names. 



Gelatine and Chondrine, etc. After prolonged boiling, the organic principles of the 

 bones, integuments, areolar tissue, tendons, and other structures composed of the white 

 fibrous tissue, are dissolved and transformed into a new substance which is called gelatine. 

 Cartilage treated in the same way is in great part converted into chondrine. The prin- 

 ciples thus formed are soluble in hot water, rendering it slightly viscid, but on cooling the 

 whole mass becomes of a more or less gelatinous consistence, according to the quantity of 

 gelatine that is present. A considerable quantity of inorganic matter, particularly phos- 

 phate of lime, is always present in combination with gelatine. 



Gelatine and chondrine present slight differences as regards their chemical reactions, 

 in other respects being nearly identical. The sulphate of alumina, alum, and the sulphate 

 of iron, will precipitate chondrine but have no influence on a solution of gelatine. Tan- 

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