THE NITROGENOUS MATTER IN MILK. 17 



because lime is more or less perfectly precipitated from its solutions, by 

 different reagents, under different circumstances. 



An important advance in our knowledge of the nature of the nitro- 

 genous matter of milk was made by the comprehensive and thorough 

 researches of 0. Hammarsten of Upsala. These researches render it highly 

 probable, that the large amount of albuminous matter which is precipi- 

 tated, at ordinary temperatures, by acetic acid, and which has long been 

 known as casein, is a characteristic albuminoid, with distinctive properties, 

 and that in addition to this body there are two other albuminoids present 

 in milk, viz., lactalbumin, and, in very small quantities, globulin. 

 Hammarsten considers casein a nucleo-albumin a body in which nuclein 

 is in complex chemical combination with albumin. According to him, the 

 chemical composition of pure casein is as follows : 



Carbon, 52-95 



Hydrogen, 7 "05 



Nitrogen, 15-65 



Oxygen, 22'78 



Sulphur, 072 



Phosphorus, 0*85 



100-00 



His lactalbumin contains neither nuclein nor phosphorus, and has 1*7 

 per cent of sulphur that is, about as much as pure egg-albumin, which 

 contains 1*6 per cent. The lactoprotein of Millon and Commaille, 

 Hammarsten considers to be made up of a mixture of imperfectly preci- 

 pitated casein, and small quantities of albumin, partially converted into 

 syntonin and peptones. He further holds that the acid character of casein 

 is due to the fact that the condition of the casein in milk depends on 

 the calcium phosphate, and that the coagulation of milk cannot take place 

 without calcium phosphate. What the nature of the relationship existing 

 between the casein and the calcium phosphate is, he does not state. 

 Eugling's assertion, that the casein is always present in milk in chemical 

 combination with normal calcium phosphate, rests on observations which, 

 on examination, do not appear to be reliable. 



According to Danilewski and Kadenhausen, milk contains no fewer 

 than seven different nitrogenous bodies, which belong to the albuminoid 

 group, or are nearly related to it. Their highly artificial theory that casein 

 is a mixture of caseo-albumin and caseo-protoalbumin bodies lacks sufficient 

 proof. 



More recently Duclaux has again revived the original theory, that 

 the albumin and the remaining nitrogenous substances are not really 

 <. M 175 ) B 



