DIET UNDER VARIOUS CONDITIONS 353 



of some of the mother's own milk or of a sterile solution of caseinogen 

 into the buttock will cause an increased supply of milk. In medical 

 practice, various lactagogues are employed to increase the flow of milk, 

 such as extract of cotton-seed. It is doubtful if the supply of milk 

 thus stimulated is adequate to the needs of the child. It is 

 probably better to supplement a deficient supply by careful artificial 

 feeding. 



Milk is a true secretion. It contains proteins and carbohydrate 

 not found in the blood-plasma. It contains, also, a proportion of 

 salts quite different to those found in the blood-plasma, the proportion 

 of some salts, such as that of calcium, being so great that they could 

 not be derived from the blood by such processes as filtration, diffusion, 

 or osmosis. The phospho-protein caseinogen probably originates 

 from the cell protoplasm of the mammary gland itself, possibly* by a 

 hydrolysis of the nucleo-protein of the gland, and subsequent synthesis 

 to caseinogen. The milk fat comes partly from the fat of the food. 

 An ingested fat, such as sesame-oil, may be traced into the milk, but 

 only in very small quantities. Most of the fat is probably formed in 

 the gland by synthesis from the components of the mammary gland, 

 probably the proteins. It is possible, also, that some is formed from 

 the carbohydrate brought in the blood to the gland. 



The origin of the mLk-sugar is not well known: possibly it is 

 formed by a rearrangement of the dextrose brought in the blood to 

 the gland. Certain drugs are secreted in the milk a fact of import- 

 ance to nursing mothers. Compounds of morphine, iodine, arsenic, 

 mercury, and iron, are among such. 



The Composition of Human Milk. Colostrum, the first secreted 

 milk, has a high specific gravity 1040 to 1060. It is richer than 

 ordinary human milk in coagulable protein (albumin), and is yellower 

 in colour. It is rich in special cellular elements, known as " colostrum 

 corpuscles." 



Human Milk is whitish-blue in colour, with a specific gravity of 

 1026 to 1036. It is amphoteric in reaction, but has a lower absolute 

 alkalinity and acidity than cow's milk. The caseinogen of human 

 milk has a slightly different chemical constitution to that of cow's 

 milk. It is said by some authorities to have a carbohydrate moiety 

 attached to it. With rennet, it yields a far less dense and uniform- 

 clot. The precipitate with weak acid is more easily soluble in excess. 

 This accounts for the greater digestibility of human milk. The pro- 

 portion of caseinogen to lactalbumin is smaller in human than in cow's 

 milk, being in human milk 2 : 1, in cow's milk nearly 6:1. The fat 

 of human milk is stated to be poorer in the volatile fatty acids than cow's 

 milk. The composition of human milk varies greatly. Its average 

 composition is probably respresented by the following figures, those 

 of cow's milk being given for comparison: 



Water. Protein. Fat. Carbohydrate. Salts. 

 Human .. .. 90-2 1-5 3-1 5-0 0-2 



Cow's .. 87-4 3-4 3-7 4-8 0-7 



