20 METABOLISM OF ORGANIC AND INORGANIC PHOSPHORUS. 



In a recent article on alkali salts in the ash of human and cow's 

 milk, Kastle a states that the practices which have for their object 

 the reduction of the amount of fat in cow's milk, or the addition 

 thereto of mineral matter available for neutralizing the acids result- 

 ing from the processes of metabolism are based on sound practical 

 experience, the important difference between the two kinds of milk as 

 to mineral constituents being as follows :,,(!) Human milk contains 

 relatively more of its mineral matter in utilizable form than cow's 

 milk; (2) it can supply the organism of the child with relatively 

 larger amounts of available alkali in proportion to the protein than 

 cow's milk. 



The idea is advanced that in the milk of various animals the inor- 

 ganic constituents are present in the same proportion as in the ash of 

 the young animals. Bunge 6 shows that there is a very close relation 

 between the composition of the ash of young rabbits, dogs, and cats, 

 and that of dog's milk, dog's blood, and dog's blood serum. He also 

 makes the statement that the epithelial cells of the mammary glands 

 select from the blood and give to the milk all the inorganic constitu- 

 ents in the proportion needed by the young animal. 



Phosphoric acid is an important constituent of milk. According 

 to the same author woman's milk contains 0.31 to 0.45 gram of phos- 

 phoric acid per liter, and cow's milk 1.81 to 1.97 grams. It is an 

 important fact that the food of the young furnishes the phosphoric 

 acid in organic combinations. 



Many investigators have shown that the phosphorus of cow's milk 

 is not so weh 1 absorbed as that of woman's milk. Stoklasa c claims 

 that the lecithin phosphorus content of woman's milk is 0.35 per cent, 

 as compared with 0.5 per cent in cow's milk. Blauberg<* fed a child 

 on mother's milk and studied the metabolism of the salts contained 

 therein. He compared his results with the results obtained by other 

 investigators and concluded that the constituents of mother's milk 

 seem to be better utilized by the system than the constituents of 

 cow's milk. 



Xo complete analyses of the mineral substances of pure, blood-free 

 muscle substance were found. The ash remaining after burning the 

 muscle (which amounts to about 10 to 15 parts per thousand, calculated 

 on the moist muscle) is acid in reaction. The chief mineral constitu- 

 ents are potassium and phosphoric acid. Next in amount are sodium 

 and magnesium, and lastly calcium, chlorin, and iron oxid. Sul- 

 phates only exist as traces in the muscles, but are formed by the burn- 

 ing of the proteins, and, therefore, occur in abundant quantities in the 

 ash. The muscles contain such large quantities of potassium and 



" Amer. J. Physiol., 1908, 22 : 284. c Zts. physiol. Chem., 1895-6, n : 79. 



&Zts. Biol., 1874, 10 : 111, 295. d Abs., Chem. Centrbl., 1897, 68 : 957. 



