58 MILK AND ITS HYGIENIC RELATIONS 



diet has less than the normal amount of fat, calcium appears 

 also in the urine. 



These observations suggest that there is some degree of 

 antagonism between a high nitrogen retention and a high retention 

 of calcium : the latter is encouraged by a high fat diet, but not the 

 former. Work on the treatment of rickets by cod liver oil seems 

 to show that one of the main advantages of this drug is to bring 

 about an improved calcium retention. 1 A discussion of this matter 

 would be beyond the scope of this work. 



Comparatively little work has been carried out on the total 

 calcium content of cows' milk. 



The relationship of calcium to caseinogen has already been 

 considered in Chap. III. 



The amount of calcium in cows' milk is many times higher 

 than that in human milk. 



Trunz (1904) investigated the composition of the ash of cows' 

 milk. He used the milk of two cows throughout a period of ten 

 and twelve months respectively. He made separate estimations 

 of the calcium combined with caseinogen and of the calcium present 

 in the form of salts. The total calcium content appears to be 

 about O'i8 to 0*19 per cent., a slight fall to about 0-154 per cent, 

 occurring after the colostral period. The amount appearing as 

 salts, i.e. not bound to caseinogen, is given as 0*13 per cent, to 0-14 

 per cent., with a drop to 0-12 per cent, in the early months. 

 Raudnitz gives 0*2 per cent, as the figure for lime content of cows' 

 milk. 



The calcium which is present in the form of salts is probably 

 mainly combined with phosphorus and with citric acid. A 

 considerable amount of work has been done upon these salts in 

 milk, but is outside the scope of this work. 



Phosphorus. It may reasonably be assumed that, as with 

 the other constituents of the milk, the milk of each species, with 

 respect to phosphorus, is specially adapted for the young of that 

 species. 



From the public health aspect, the phosphorus content of milk 

 does not appear to be as important as the content of other con- 

 stituents, since the phosphorus content of cows' milk is greatly in 

 excess of that in human milk, so that the human infant fed on 

 cows' milk receives a plentiful supply of phosphorus. 



The phosphorus is present in several forms in caseinogen, as 

 salts, and also in lecithin. 



Siegfried states that in cows' milk 6 per cent, of the total phos- 

 phorus is combined with caseinogen, and in human milk 41-5 per 

 cent., this latter milk containing relatively little inorganic phos- 

 phorus. The high lecithin content found in human milk by 

 Stocklasa has already been mentioned. 



1 Cp. Schabad and Sorochowitsch and others. 



