334 



PHYSIOLOGICAL CHEMISTRY 



composition of human milk at different periods is represented in the 

 following table. 1 



PERCENTAGE COMPOSITION OF HUMAN MILK BY PERIODS 



The composition of the ash of milk is shown in the following table 

 reported by Holt, Courtney and Fales. 2 



PERCENTAGE COMPOSITION OF THE ASH OF MILK 



It will be observed that the composition of the ash of the two varieties 

 of milk is about the same except for phosphorus. The higher phos- 

 phorus content in the case of cow's milk is due principally to the fact 

 that the milk contains a higher percentage of casein or phospho protein. 

 It should be borne in mind that cow's milk contains on the average 

 over three times as much ash as human milk. Therefore unless cow's 

 milk has been diluted with more than twice its volume, there is still 

 present as high a concentration of the inorganic constituents as are 

 , present in normal human milk. Hence there is no necessity for the 

 addition of any of these constituents in infant feeding. 



Interesting data relative to the composition of milk from various 

 sources may be gathered from the following table which was compiled 

 mainly from the results of investigations by Proscher 3 and by Abder- 

 halden 4 in Bunge's laboratory. It will be noted that the composition 

 of the milk varies directly with the length of time needed for the young 

 of the particular species to double in weight. 



1 Holt, Courtney and Fales: Am. Jour. Dis. Children, 10, 229, 1915. 



2 Holt, Courtney and Fales: Am. Jour. Dis. Children, 10, 229, 1915. 



3 Proscher: Zeit.f. physiol. Chemie, 24, 285, 1898. 



4 Abderhalden: Ibid., 26, 487, 1899; and 27, pp. 408 and 457, 1899. 



