HUMAN MILK. 661 



while among the solid fatty acids myristic and palmitic acids are found 

 to a greater extent than stearic acid. 



The essential qualitative difference between woman's and cow's milk 

 seems to lie in the proteins or in the more accurately determined casein. 

 A number of both the earlier and more recent investigators l claim that 

 the casein from woman's milk has other properties than that from cow's 

 milk. The essential differences are the following: The casein from 

 woman's milk is precipitated with greater difficulty with acids or salts. 

 It does not coagulate uniformly in the milk after the addition of rennet, 

 which depends, essentially, upon the low amount of lime-salts and casein 

 contained in the milk. 2 It may be precipitated by gastric juice, but 

 dissolves completely and easily in an excess of gastric juice; the casein pre- 

 cipitate produced by an acid is more easily soluble in an excess of the acid; 

 and lastly, the clot formed from the casein of woman's milk does not 

 appear in such large and coarse masses as in the casein from cow's 

 milk, but is more loose and flocculent. This last-mentioned fact is of 

 great importance, since it explains the generally admitted fact of the 

 easy digestibility of the casein from woman's milk. 



The question as to whether the above-mentioned variations depend 

 on a decided difference in the two caseins, or only on an unequal relation 

 between the casein and the salts in the two kinds of milk, or upon other 

 circumstances, has not as yet been decided. According to SZONTAGH 

 and- ZAITSCHEK and also WR6BLEWSKY, the casein from human milk 

 does not yield any pseudonuclein on peptic digestion, and hence it cannot 

 be a nucleoalbumin. According to KOBRAK, woman's casein yields 

 some pseudonuclein, and with repeated solution in alkali and precipitation 

 by an acid it becomes more and more like cow's casein. He therefore 

 suggests the possibility that woman's casein is a compound between a 

 nucleoalbumin and a basic protein. WR6BLEWSKY found the follow- 

 ing for the composition of casein from woman's milk: C 52.24, H 7.32, 

 N 14.97, P 0.68, S 1.117 per cent. LANGSTEIN and BERGELL obtained 

 much lower figures for N, S and especially P, namely, 14.34, 0.85 and 0.27 

 per cent, respectively. According to LANGSTEIN and EDELSTEIN the 

 phosphorus content is only 0.22-0.29 per cent. On hydrolysis ABDER- 

 HALDEN and LANGSTEIN 3 could not find any difference between cow 

 and human casein. 



^ee Biedert, Untersuchungen iiber die chemischen Unterschiede der Menschen- 

 und KuhmiHh (Stuttgart), 1884; Langgaard, Virchow's Arch., 64; Makris, Studien 

 iiber die Eiweisskorper der Frauen- und Kuhmilch, Inaug.-Diss. Strassburg, 1876. 



2 See among others Bienenfeld, Bioch. Zeitschr., 7, and Fuld and Wohlgemuth, 

 ibid., 8. 



3 Szontagh, Maly's Jahresber., 22; Zaitschek, 1. c.; Wr6blewsky, Beitrage zur 

 Kenntniss des Frauenkaseins, Inaug.-Diss. Bern. 1894, and Ein neuer eiweissartiger 



