CHAP. XLIV.] MILK. 629 



quantity of saccharine and oily materials. In it albumen is often 

 detected. This is called the colostrum. The specific gravity varies 

 from 1020 to 1045. 



The oil existing in milk, occurs in a state of minute division, 

 in the form of oil-globules, which are equally diffused throughout 

 the fluid. These oil-globules are each invested with a delicate 

 membranous envelope, composed of caseine, which prevents their 

 running together. If milk and ether be shaken and well 

 mixed, the oily constituents are not dissolved, in consequence 

 of the envelope of caseine with which they are invested ; but if, 

 previous to the addition of the ether, a little acetic acid or alkali, 

 or alkaline salt, which has the power of dissolving the covering, 

 be added, the globules are immediately dissolved, and the milk 

 becomes perfectly clear. By churning, the envelopes are rup- 

 tured, and the oil-globules are made to run together, forming 

 butter. 



If the slightly turbid solution from which the cream has been 

 removed be allowed to stand for some time, or if an acid be added 

 to it, a flocculent precipitate occurs. This is caseine, which is 

 coagulated by all acids. It is, however, not coagulated by heat ; 

 but during evaporation, a scum forms upon the surface of solutions 

 containing caseine. 



The following analyses show the chemical composition of human 

 milk. Specific gravity, 10301034. 



Colostrum. Sij 9 days. 12 days. Average. 



Water . . . 828-0 . . . 879-848 . . 885-818 . . 905-809 . . 891-0 



Solid matter . 172-0 . . . 120-152 . . 114-182 . . 94-191 . . 109-0 



Albumen . . 40'0 caseine 35-333 . . 36*912 . . 29-111 . . 337 



Butter . . . 50-0 . . . 42-968 . . 35-316 . . 33*454 . . 37-1 



Sugar of milk 70'0 . . . 41-135 . . 42-979 . . 31-537 . . 38'5 



Salts .... 3-1 ... 2-095 . . T691 . . 1-939 . . 1-9 



The first two analyses are by Franz Simon, and the last three 

 by Clemm. 



Cow's milk contains more caseine and less sugar than human 

 milk. Ass's milk contains less butter and less caseine, but more 

 sugar ; while in goat's milk the caseine preponderates over the 

 other constituents. L'Heretier has shown that temperament 

 exerts an influence upon the character of the milk. The average 

 quantity of solid matter in 1000 parts of milk from fair women, 

 was 120 grains; and of brunettes, as much as 134 grains. 



The characters of the milk, also, it need hardly be said, are 



