48 THE SECRETIONS: 



albumen coagulated. The presence of casein was shown, and 

 its amount determined, by the addition of acetic acid, by 

 boiling the fluid till it evaporated to the consistence of an 

 extract, and by then extracting it with boiling spirit. The 

 casein differed from the ordinary casein of cow's milk, in being 

 soluble to a very considerable extent in boiling spirit ; it par- 

 tially separated from the clear hot solution on cooling : it 

 seemed rather to resemble the casein of the crystalline lens. 

 After the removal of the fat, by means of ether, it was almost 

 perfectly soluble in water; on the application of heat, the 

 surface of the solution became covered with an irregular film, 

 and the addition of a little dilute acid was followed by a very 

 copious precipitate. 



The analysis of this milky fluid yielded, in 1000 parts : 



Analysis 61. 



Water 737-00 



Solid constituents 

 Fat 

 Casein 

 Albumen 



263-00 



7-98 



28-93 



198-34 



Extractive matters, traces of sugar and casein, chloride of 



sodium, and lactate of soda . . . 18*41 



The milk of the same ass was examined eight days after- 

 wards ; it was less thick and sticky, and rather whiter than 

 before. It more closely resembled true milk in its smell, and 

 it had a mild, faintly sweet taste. It contained, in 1000 parts : 



Analysis 62. 



Water . . . . . 814-0 



Solid constituents .... 186*0 



Fat ..... 8-5 



Casein . . . . 25-0 



Albumen .... 123-9 



Extractive matter, with a little sugar, salts . . 28-6 



The change in the constitution of the fluid was very striking ; 

 the solid constituents collectively, and especially the albumen, 

 were diminished, while the fat, casein, and sugar, had relatively 

 increased. In the first analysis, the casein formed only one 

 ninth of the solid residue ; in the second, it amounted to one 

 seventh. 



Lassaigne has observed similar proportions in the fluid 

 secreted by the mammary glands of cows previous to calving. 

 Forty-one days before calving, it contained albumen in place 



