THE INORGANIC CONSTITUENTS OF MILK 49 



CHAPTER IV 



ON THE INORGANIC CONSTITUENTS OF MILK 



Total Ash. A large number of figures dealing with the total 

 ash have already been given in the preceding sections. 



The ash content of cows' milk is in all cases considerably higher 

 than that of human milk, so that the infant which is artificially 

 fed on undiluted cows' milk does not suffer from lack of total 

 ash. Variations appear in the amount found by various authors, 

 especially among the earlier workers, but in no case does the varia- 

 tion obliterate the marked difference between the total amounts 

 of ash in the two classes of milk. 



Although there can be no doubt that all the inorganic materials 

 present are needed for the life of the organism, certain of the con- 

 stituents have received much closer investigation than others. 

 The sodium, potassium, magnesium, &c., have been estimated 

 both for cows' and for human milk, by Bunge, Camerer and Soldner, 

 and others, and many of the figures have already been given. 1 



More detailed investigations have been carried out on the 

 calcium, iron, and phosphorus content of both human and 

 cows' milk, and in view of the importance of these constituents, 

 it will be necessary to consider them in detail under separate 

 headings. 



Iron. The iron content of milk is a subject of much im- 

 portance and of considerable interest. 



The investigations made by the earlier workers give results 

 which are so different from one another as to leave the reader of 

 their papers in some degree of despair. 



The chief source of discrepancy lies in the difficulty of securing 

 an accurate estimation of the minute quantities of iron that are 

 present. Until a few years ago the methods used necessitated 

 a preliminary desiccation and ashing of large quantities of fluid, 

 and any error was accentuated owing to the very small amounts 

 found. 



The colorimetric method of recent years has produced much 

 more satisfactory results. Soxhlet states that it is correct to 

 within 10 per cent., which, although a high percentage of error, 

 is comparatively immaterial on the minute quantities concerned. 



The fact of primary importance to be decided is whether cows' 

 milk contains as much iron as human milk, and if not, how great 

 the deficit, and whether this can be repaired. 



A very interesting account of the history of the work upon 



1 See p. 1 8. 



