MILK 



315 



The milk-curdling enzymes of the gastric and the pancreatic juice 

 have the power of splitting the casein of the milk, through a process of 

 hydrolytic cleavage, into soluble paracasein and a peptone-like body. 

 This soluble paracasein then forms a combination with the soluble 

 calcium salts of the milk and an insoluble curd of paracasein results. 

 The clear fluid surrounding the curd is known as whey. This action 

 of rennin may be represented by the following scheme : 



Casein (+ rennin) 



L 



Peptone-like 

 body 



Soluble paracasein 



+ Ca salts 



I 

 Paracasein 



(insoluble curd) 



FIG. 103. NORMAL MILK AND COLOSTRUM. 

 a, Normal milk; b, Colostrum. 



There is still considerable confusion of terms when different authori- 

 ties discuss milk proteins and the action of milk curdling enzymes upon 

 them. The English scientists 1 quite uniformly call the principal pro- 

 tein of milk caseinogen whereas the insoluble curd formed by rennin is 

 termed casein. On the other hand, the Germans and many Americans 

 give the name casein to the milk protein and paracasein to the product 

 of the action of rennin upon this protein. The confusion of terms 

 may be represented thus: 



English German. 



Caseinogen. = Casein. 



Casein. Paracasein. 



1 Halliburton: Journal of Physiology, n, 448, 19- 



