310 HANDBOOK OF PHYSIOLOGY. 



few days after parturition is called the colostrum. This contains the 

 granular colostrum corpuscles, which are four or five times the size of 

 milk globules, and differs from ordinary milk in containing a larger 

 quantity of solid matter, and in being deep yellow, less sweet, but far 

 more alkaline, and in having a specific gravity of 1040-104G. 



COMPOSITION OF COLOSTRUM (Pfeiffer). 



Proteids 5.71 



Fat 2.04 



Sugar 3.74 



Salts 0.28 



Water .... 88.23 



100.00 



Chemical Composition of Milk. In addition to the oil existing in 

 numberless little globules floating in a large quantity of water, milk 

 contains certain proteids, milk-sugar (lactose), and several varieties of 

 salts. Its percentage composition has been already mentioned, but may 

 be here repeated. Its reaction is slightly alkaline. 



CHEMICAL COMPOSITION OF MILK. (After Foster, Harrington, et al. ) 



Water 

 Solids 



Fats 

 Proteids 

 Sugar 

 Salts . 



Constituents of Milk. 



(1.) Water. The amount of water varies in different animals, and 

 in the same animal from time to time. This is seen from the varying 

 specific gravity; that of cow's milk, on the average, varies from 1028 to 

 1034 in unskimmed milk, and from 1033 to 1037 in skimmed milk. 

 The amount secreted by a woman is from 10 to 16 oz. at the end of the 

 first week of lactation, and increases to from 30 to 40 oz. by the eighth 

 or ninth month. A cow under favorable circumstances secretes at least 

 ten pints a day. 



(2.) Proteids. These are of two kinds at least, viz., caseinogen and 

 lact-albumin . Caseinogen may be obtained from milk either by the 

 addition of an acid, e.g., acetic, or by saturation with crystallized mag- 

 nesium sulphate or sodium chloride in the way already indicated (p. 

 119). Caseinogen, as already pointed out, belongs to the class of 

 nucleo-albumins (see p. 119). 



Coagulation of Milk. The clotting of caseinogen is seen when the 

 gastric ferment rennin, or when similar ferments from the pancreas or 

 intestinal juice are added to milk; it will take place when the milk is 



