1024 OF GENERATION. 



sets of compounds, one of them soluble in water, the other insoluble ; the latter 

 being formed only when the quantity of acid is large in proportion to the casein. 

 Thus, when two fluid ounces of Cow's milk were boiled with a single drop of 

 nitric acid, complete coagulation of the casein at once took place : but when two 

 fluid drachms of Human milk were treated in the same manner, no coagulation 

 occurred, though the casein was at once thrown down by a solution of lerrocy- 

 anide of potassium; the same quantity of milk, with five drops of the acid, 

 formed a coagulum which was not very manifest until after the lapse of five 

 hours, but was very complete, the serous fluid not being found to contain any 

 casein by testing it with ferrocyanide of potassium ; and it required ten drops 

 of nitric acid to produce immediate coagulation. The quantity of acid necessary 

 to produce coagulation sufficiently rapid to be immediately visible will vary with 

 the amount of casein present in the particular specimen of milk, 5 drops in some 

 instances producing a coagulation as rapid as that produced by 10 drops in 

 others. In no specimen did Mr. Moore fail to produce coagulation by adding 

 a sufficiency of acid. Acetic acid without heat produces in Human milk a 

 slow separation of soft flaky coagula ; but, when heat is employed, a more perfect 

 coagulation is produced by small than by large quantities of this acid. Rennet 

 does not seem to act upon the casein of Human milk, unless an acid be also 

 present. In several of these particulars, as well as in its small proportional 

 amount, the Casein of Ass's milk bears a closer resemblance to that of Human 

 milk than does that of the Cow. The Sugar of Milk, which may be obtained 

 by evaporating whey to the consistence of a syrup, and then setting it aside to crys- 

 tallize, forms opaque prisms or rhombohedra, whose composition is 10C,8H, 

 80 -f 2HO. In many of its properties it bears a close resemblance to Glucose 

 ( 45), into which it is readily converted by the agency of dilute sulphuric or 

 hydrochloric acid, or by the acetic or citric acids. It is readily made to pass 

 into the lactic and butyric fermentation, by the appropriate ferments ; but is 

 with difficulty brought to undergo the vinous fermentation. The Saline matter 

 contained in milk appears to be nearly identical with that of the blood ; with a 

 larger proportion of the phosphates of lime and magnesia, which amount to 2 or 

 2 parts in 1000. These phosphates are held in solution chiefly by the casein, 

 which seems to have a power of combining with them, even greater than that 

 of albumen : the presence of a minute proportion of free alkali, also, assists their 

 solution. A small portion of iron in the state of phosphate, together with the 

 chlorides of potassium and sodium, may also be detected in milk. 1 



1025. The proportion of these different constituents is liable to great varia- 

 tion, from several causes. Thus, the whole amount of the solid constituents 

 may vary from 86 to 138.6 parts in 1000 ; the difference being partly due to 

 individual constitution, but in great part, also, to the amount and character of 

 the ingesta. The average seems to be between 100 and 120 parts. The follow- 

 ing are the results of the analyses of Simon ; the first column being the average 

 of fourteen observations upon the same woman ; the second giving the maxi- 

 mum of each ingredient ; and the third the minimum : 



i. ii. in. 



Water 883.6 914.0 861.4 



Butter 25.3 54.0 8.0 



Casein 34.3 45.2 19.6 



Sugar of Milk and extractive matters . . 48.2 62.4 39.2 



Fixed salts 2.3 2.7 1.6 



It also appears, from the analyses of Simon, that the proportion of the different 

 ingredients is liable to variation, according to the time which has elapsed since 

 parturition. The quantity of Casein is at its minimum at the commencement of 



1 Haidlen in " Annalen der Chemie und Pharmacie," band xlv. p. 263. 



