28 MILK [m 



also been called albuminose or galactine ; and lacto- 

 globulin. 



Casein. According to Kirchner, casein (i.e. casein 

 proper) varies from 2 to 4'5 per cent, and is, on an 

 average, present in milk to the extent of 3 '2 per cent. 

 Its percentage composition is as follows : 



Carbon . . . . 53-00 



Hydrogen . . . . 7 '12 



Nitrogen . . . . 15-65 



Oxygen . . . . 22-60 



Sulphur . . . -78 



Phosphorus . . . -85 



100-00 



From the above it will be seen that milk casein 

 contains both sulphur and phosphorus. Casein is 

 characterised by the presence in it of a substance 

 called nuclein, a body not found in albumin. What 

 is usually known as the casein in milk is not, as we 

 already mentioned, pure casein, which is a body 

 insoluble in water. There seems to be no doubt that 

 the casein, in milk, is combined in some way with 

 lime. This compound, which, as we have said, is 

 sometimes called caseous matter or caseinogen, differs 

 from pure casein by being more soluble. It is not, 

 however, strictly speaking, soluble in water, but 

 forms with it a bulky, colloidal (or glue-like) mass. 

 This is proved by the fact that if niilk be filtered 

 through porous clay the caseous matter does not pass 



