i MILK ii 



alkali metals. There must therefore be another acid present in 

 the milk, and that an organic one. Such an acid has been 

 shown by Hcnkel l to be a constant constituent of milk, arid he 

 proved it to be citric acid. By calculation, it is found that 

 about 0*25 per cent, citric acid is necessary to combine with 

 the residual lime. Recent investigations by Beau 2 lead to the 

 conclusion that the amount of citric acid in milk is on an 

 average 0'2 per cent. 



According to Soldner, 3 the milk salts would be present in the 

 following proportions in the milk : 



100-00 per cent. 



The salts are present in the milk in a completely dissolved 

 state, with the exception of a part of the calcium phosphate 

 which is there as a solid in a finely-divided form. 



Amongst the other constituents of milk are certain chemical 

 substances which are found there either constantly or acci- 

 dentally, as well as solid bodies which also may be present 

 regularly or irregularly. Amongst those substances which are 

 constantly found in milk, although only in very small quantities, 

 mention may first be made of lecithin. This substance, in 

 spite of the insignificant amount which is present, is of very 

 great physiological importance. 



From the investigations of F. Bordas and Sig. de Raczkowski 4 

 it is known that 0*065 g. of lecithin is the average quantity 

 found in 100 c.c. of milk, but this amount varies with the 

 period of lactation, and in such a manner that immediately 



1 " Zitronensiiure als normales Bestandteil dcr Milch," Die Landivirtach. 

 VermtchmstatioH., 1891, Vol. XXXIX, p. 143. 



2 Revue Gentrale du Lait, Vol. Ill, 1904, p. 385. 



3 "Die Salze der Milch und ihre Beziehungen zu dem Verhalten des 

 Kaseins," Die Landivirtach. VersucJwitation. , 1888, Vol. XXXV, p. 361. 



4 Compt. rend, de VAcad. des Sciences, Vol. CXXXIV, p. 1592, and Vol. 

 CXXXV, pp. 302 and 354. 



