488 LEGUMIN. 



line phosphates), when exactly neutralized, in the form 

 of a flocculent, fibrous, non-gelatinous mass. In an 

 alkaline solution and in the milk, it is not coagulated 

 by boiling ; the solution only forms a skin of coagu- 

 lated casein on the surface, which, when removed, is re- 

 formed. When a slightly alkaline solution of casein 

 is poured into an excess of an acid, a flocculent pre- 

 cipitate is formed, which is soluble in pure water. 

 This is a compound of casein with the acid employed. 

 The real coagulation of casein is brought about in a 

 peculiar manner, as yet not satisfactorily explained : 

 i. e., by contact with the internal mucous membrane 

 of the stomach of the calf. Skimmed milk, warmed 

 with a small piece of such a stomach (rennet) at 

 50-60, coagulates so thoroughly, that only very small 

 quantities of casein remain in a state of solution in 

 the whey. The coagulum formed in this way, mixed 

 with fat, forms cheese, when dried. 



In a coagulated condition casein resembles coagu- 

 lated albumen in nearly all its properties. 



3. Legumin. In leguminous and many other seeds, 

 a protein compound, very similar to casein, is con- 

 tained. In order to prepare it, beans or lentils are 

 softened with warm water and triturated to a paste. 

 This paste is then diluted with water and the skins 

 sieved off. Legumin, in a state of solution, is con- 

 tained in the liquid that passes through the sieve ; 

 starch, in a state of suspension, is also contained in it, 

 but the latter is deposited if the liquid is allowed to 

 stand quietly. By adding a very little acetic acid, the 

 legumin is thrown down as a gelatinous mass ; to 

 purify it, it is washed out with water, alcohol, and 

 ether. The crude solution soon becomes acid, if left 

 alone, on account of the formation of lactic acid ; and 

 thus coagulates spontaneously. It does not coagulate 

 when boiled, but, as in the case of milk, a skin is 

 formed on the surface, which is always reformed when 

 removed. The dissolved condition of legumin ap- 

 pears, as in the case of casein, to be caused by the 

 presence of alkalies. "When oily seeds (e. g., shelled 



