HUMAN MILK. 627 



Human Milk. 



Woman's milk is amphoteric in reaction. According to COURANT its 

 reaction is relatively more alkaline than cow's milk, but it has nevertheless 

 a lower absolute reaction for alkalinity as well as for acidity. He found 

 between the tenth day and the fourteenth month after confinement prac- 

 tically constant results. The alkalinity, as well as the acidity, was a 

 little lower than in childbed. One hundred cc. of the milk had the same 

 average alkalinity as 10.8 cc. N/10 caustic soda, and the same acidity 

 as 3.6 cc. N/10 acid. The relation between the alkalinity and the 

 acidity in woman's milk was as 3:1, and in cow's milk as 2.1:1. The 

 actual reaction determined electrometrically is, according to Fol, 1 still 

 nearly neutral, like the other kinds of milk. 



Human milk also contains fewer fat-globules than cow's milk, but 

 they are larger in size. The specific gravity of woman's milk varies 

 between 1.026 and 1.036, generally between 1.028 and 1.034. It is highest 

 in well-fed and lowest in poorly fed women. The freezing-point is lowered 

 on an average 0.589 C., according to WINTER and PARMENTIER 2 constant 

 at 0.55, and the molecular concentration is 0.318. 



The fat of woman's milk has been investigated by RUPPEL. It forms a 

 yellowish-white mass, similar to ordinary butter, having a specific gravity 

 of 0.966 at 15. It melts at 34.0 C. and solidifies at 20.2 C. The fol- 

 lowing fatty acids can be obtained from the fat, namely, butyric, caproic, 

 capric, myristic, palmitic, stearic, and oleic acids. The fat from woman's 

 milk is, according to RUPPEL and LAVES, S relatively poor in volatile fatty 

 acids. The non-volatile fatty acids consist of one-half oleic acid, 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 4 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. 5 It may be precipitated by gastric juice, but 



1 Compt. rend. soc. biolog., 58. 



2 See Maly's Jahresber., 34. 



3 Ruppel, Zeitschr. f. Biologic, 31; Laves, Zeitschr. f. physiol. Chem., 19. 



4 See Biedert, Untersuchungen liber die chemischen Unterschiede der Menschen- 

 und Kuhmilch (Stuttgart), 1884; Langgaard, Virchow's Arch., 65; Makris, Studien 

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



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

 ibid., 8. 



