310 MILK AND MILK PRODUCTS. XIV. 



casein and albumin ; Halliburton" also gives two caseinogen 

 and albumin. 



Engling and Sebelienf in addition found globulin. Dani- 

 lewsky and Radenhausen (1880) described at least five proteids 

 as present in milk. The presence of casein or caseinogen, 

 albumin, and globulin is generally admitted, while one or two 

 others are possibly present in very small proportion. 



Casein or, according to modern nomenclature, cascinogen, is 

 a white amorphous body, devoid of taste or smell, insoluble in 

 water, alcohol, or ether, soluble in dilute alkalies or solutions 

 of alkaline carbonates or phosphates. It is insoluble in dilute 

 but dissolves in strong acids. 



It is capable of uniting with calcium salts, particularly the 

 phosphate, with which it is associated in milk and from which 

 it is freed with difficulty. 



According to Halliburton's nomenclature, casein is the name 

 given to the curd formed by the action of rennet upon milk. 

 In the milk caseinogen exists and can be precipitated by acids. 



Various analyses of casein have been published. The follow- 

 ing by Chittenden and Painter may be taken as typical : 



% 

 Carbon ... ... 53-30 



Hydrogen ... ... 7'07 



Oxygen ... ... 22-03 



Nitrogen ... ... 15'91 



Phosphorus ... ... 0'87 



Sulphur ... ... 0-82 



Caseinogen is capable of coagulation in two ways by the 

 action of an acid, less acid being required at high than at low 

 temperatures ; or by the action of the enzyme contained in 

 rennet known as rennin, lab, chymosin, or pixine. This fer- 

 ment is found in the stomachs of a large number of animals, 

 being generally more abundant in young than in adult indi- 

 viduals. It or a ferment possessed of similar powers is found 

 in birds, fishes, and in many plants ; also as a product of the 

 action of certain bacteria. In the case of acid coagulation the 

 curd formed consists of the unaltered caseinogen and is almost 

 free from calcium compounds. 



* Chemical Physiology. t Jour. Soc. Chem. Iml. 1886, 387. 



