MILK. 313 



gravity of woman's milk is between 1.026 and 1.035, but varies 

 generally between 1.028 and 1.034. This milk in general has a less 

 inclination to turn acid, and it therefore does not coagulate dis- 

 tinctly. 



The fat from human milk has not been thoroughly investigated. 

 According to HOPPE-SEYLER, it is richer in fluid fats than the fat 

 from cow's milk. 



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

 milk seems to lie in the proteids, or in the more accurately deter- 

 mined casein. A number of investigators, such as BERZELIUS, 

 SIMON, BIEDERT, LANGGARD, MAKRIS, and others, 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 regularly in the milk 

 after the addition of rennet ; it may be precipitated by gastric 

 juice, but dissolves completely and easily in an excess of the same; 

 the casein precipitate produced by an acid is more easily soluble in 

 an excess of the acid ; and lastly, the clot formed from the casein 

 does not appear in such large and coarse masses as 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 

 easy digestibility of the casein from woman's milk. The question 

 as to whether the above-mentioned differences depend on a decided 

 difference in the two caseins or only on an unequal relationship be- 

 tween the casein and the salts in the two varieties of milk, or 

 upon other circumstances, has not been sufficiently investigated, 

 and doubtless further experiments will be of great value. We 

 have not, up to the present time, any quite trustworthy analyses of 

 the casein from woman's milk, but it seems probable that the 

 caseins from woman's and cow's milk are not identical albuminous 

 bodies. Besides casein, woman's milk contains lad albumin, and 

 certain investigators maintain that they have found relatively large 

 amounts of albumoses and peptones. According to other state- 

 ments (DOGIEL and HOFMEISTER), no peptones occur in woman's 

 milk, and the methods employed for detecting albumoses seem to 

 have given no positive results. The albuminous bodies of woman's 

 milk require more thorough investigation. The total quantity of 



