CHEMICAL CONSTITUENTS OF BODY AND FOOD. 43 



which prevents the alkali from decomposing the casein. It is then 

 dried, and is a yellowish-white body. It contains 2 per cent, of fat 

 and milk-sugar and 7 per cent, of salts. It is used as a substitute for 

 milk when a large amount of water is not desirable. 



The fats of milk are olein, palmitin, stearin, caproin, and buty- 

 rin. The milk of women contains twice as much olein as palmitin 

 and stearin, but these bodies are about the same in quantity in cows' 

 milk. In cows' milk two-fifths is olein, one-third is palmitin, one- 

 sixth stearin and butyrin, and caproin one-fourteenth of the total 

 fat. 



Buttermilk contains about 10 per cent, of solids, including 

 casein; lactose; and about 1 per cent, of fats. 



Butter is formed in churning by making the fat-particles adhere 

 to each other, forming a yellow, fatty mass. 



The salts of milk average 0.6 per cent, and they consist chiefly 

 of phosphate of lime with calcium chloride, magnesium phosphate, 

 and traces of iron. 



Milk also contains about 7.6 per cent, of carbonic acid and traces 

 of oxygen and nitrogen. 



The quantity of milk daily secreted by a woman is about one 

 quart. 



The quantity of milk changes during lactation, which lasts in the 

 woman about ten months. In the case of the woman, the percentage 

 of casein and fat increases to the end of the second month, but sugar 

 lessens even in the first month. During the fifth to the seventh 

 month there is a diminution of fat, and between the ninth and tenth 

 months a decrease of casein. In the first five months the salts 

 increase; after that they diminish. 



Colostrum is the milk secreted for a few days after parturition, 

 and it has peculiar characteristics. It contains large corpuscles called 

 colostrum-corpuscles, which are large cells full of colorless, fatty par- 

 ticles. 



A poisonous principle is sometimes generated in milk by microbes. 

 It is called tyrotoxicon. 



VEGETABLE FOODS. 



Vegetable substances differ very much from animal bodies in their 

 physical appearances, and, in some respects,* also chemically. The 

 vegetable matters are capable of being transformed into the various 

 animal components and thereby nourish the animal body, since they 

 contain all the elements, or proximate principles, that are necessary 



