COMPOSITION OF MILK. 383 



contains numerous peculiar structural elements which finally 

 quite disappear from the secretion, but which are of considerable 

 interest in relation to the physiological process of the secretion. 

 These are the colostrum corpuscles, which consist of large spheri- 

 cal masses of fine fat globules held together by the remains of a 

 gland cell, which incloses the fat globules as a kind of sack or 

 case, and in which at times a nucleus can be made out. 



The most remarkable point about the chemical composition of 

 milk as a secretion is the large proportion of proteid and fat it 

 contains. It appears that there are two distinct albuminous bodies 

 present, viz.: casein, which appears identical with alkali albumin, 

 and another form of albumin allied to serum albumin. The fats 

 are present in the shape of globules of various sizes, being in the 

 condition of a perfect emulsion, as above stated. They consist 

 of glycerides of palmitic, stearic, and oleic acids. 



The milk sugar is very like glucose or grape sugar, but 

 not so soluble. It has the peculiarity of undergoing lactic 

 fermentation. 



Of the inorganic constituents of milk the most important are 

 sodium chloride, and phosphates and carbonates of the alkalies ; 

 and it is a remarkable fact that the potash compounds, which are 

 the most abundant in the red blood corpuscles, are present in 

 greater quantity than those of soda. 



The following table shows the composition of human milk, a 

 comparison of which with that of some domestic animals will be 

 found 011 page 103 : 



Albumin, 39.24 



Fat, 26.66 



Milk sugar, 43.64 



Salts, ' 1.38 



110.92 

 Water, 889.08 



1000.00 



The relative quantity of the several ingredients of milk varies 

 with the kind of diet used. A vegetable diet increases the per- 

 centage of sugar, but diminishes that of the other constituents, and 



