974 OF GENERATION LACTATION. 



milk was no longer required, great difficulty was experienced in arresting 

 the secretion. His genital organs were fully developed." Corresponding 

 facts are also recorded of the male of several" of the lower animals. 



811. The secretion of Milk consists of Water, holding in solution Sugar, 

 various Saline ingredients, and the peculiar albuminous substance termed 

 Casein ; and having Oleaginous particles suspended in it. Its reaction is 

 sometimes alkaline, sometimes neutral, and sometimes acid. Cow's milk is 

 usually, and the milk of Carnivora always, acid, 1 from the presence of free 

 lactic acid. The constitution of this fluid is made evident by the ordinary 

 processes to which it is subjected in domestic economy. If it be allowed to 

 stand for some time, exposed to the air, the greater part of the oleaginous 

 globules come to the surface, being of less specific gravity than the fluid 

 through which they are diffused : this is especially the case with the larger 

 faceted globules, which have been hence distinguished as "cream globules." 

 The cream thus formed does not, however, consist of oily particles alone; 

 but includes a considerable amount of casein, with the sugar and salts of the 

 milk. These are further separated by the continued agitation of the cream ; 

 which, by rupturing the envelopes of the oil-globules, separates it into butter, 



FIG. 370. 



Microscopic appearance of Human Milk, with an intermixture of Colostric corpuscles at a a, and 



elsewhere. 



formed by their aggregation, and buttermilk, containing the casein, sugar, 

 etc. A considerable quantity of casein, however, is entangled with the ole- 

 aginous matter, and this has a tendency to decompose, so as to render the 

 butter rancid ; it may be separated by keeping the butter melted at the 

 temperature of 180, when the casein will fall to the bottom, leaving the 

 butter pure and much less liable to change. The milk, after the cream has 

 been removed, still contains the greatest part of its casein and sugar. The 

 amount of casein and of fat increases when milk is allowed to stand for 

 twenty-four hours, the former at the expense of the albumen, 2 and the latter 

 under the influence of fungi. Thus Kemmerich found in colostrum imme- 

 diately after withdrawal 31 parts of casein, and 43^- parts of albumen, but 

 after the lapse of 24 hours these proportions were reversed, the quantities 



1 V. Gorup-Bosanoz, p 888. See in regard to the Comparative Chemistry of the 

 Cow and Goat, Bogomoloff, Centra! hlatt, 1871, p. G25. 

 1 Kemmerich, Pfluger's Archiv, Bd. ii, p. 401. 



