CHAP. I.] CASEINE. 39 



tate occur s, which is sulphate of caseine. By digesting the clot, thus 

 formed, with water and carbonate of lime, the acid combines with 

 the lime, and the caseine, set free, dissolves in the water, and may 

 be obtained by evaporation. 



Caseine is coagulated very perfectly by the action of rennet (the 

 fourth or true digesting stomach of the calf) aided by heat. This 

 power of coagulating caseine is not to be attributed to the acid of 

 the calf's stomach, but to the organic principle (pepsine) resident 

 in it ; for the power remains, after all evidence of acid reaction has 

 been removed. This is one of the most powerful agents in causing 

 the coagulation of caseine, and it has been employed in domestic 

 oeconomy for the manufacture of cheese, which consists of the curd 

 mixed with butter, compressed and dried. So perfect is the coagu- 

 lating power of rennet, that not a particle of caseine in milk sub- 

 mitted to its action will remain uncoagulated. 



Caseine comports itself with reagents in a manner very similar 

 to albumen. In the coagulated state it is insoluble in water, but 

 soluble in liquor potassae. It is not precipitated by heat alone, in 

 which respect it differs from albumen. Acetic acid, which will 

 not precipitate albumen, causes the coagulation of caseine, and an 

 excess of acid again dissolves it. 



Caseine contains sulphur, but no phosphorus. 



Mulder's ultimate analysis is as follows : 



Nitrogen .... 15-95 



Carbon . . . . 55-10 



Hydrogen .... 6*97 



Oxygen. . . . 21-62 



Sulphur .... 0-36 



100-00 



If albumen, or fibrine, or caseine, be dissolved in a moderately 

 strong solution of caustic potash, and exposed for some time to 

 a high temperature, it becomes decomposed; and if acetic acid 

 be now added, a precipitate takes place of a gelatinous trans- 

 lucent matter. This substance was discovered by Mulder, and 

 named by him Proteine (from the Greek verb Trpwreva), I am first), 

 as being the radicle of these proximate principles ; or, in the lan- 

 guage of Liebig, the commencement and starting-point of all the 

 tissues: so that it appears that each of these principles is com- 

 posed of this substance, with the addition of certain proportions of 

 phosphorus, sulphur, or of both. In the process by which it is 

 obtained, the object is to remove the sulphur and phosphorus 



