MILK SECRETION 27 



great joy or grief. Similarly the nervous condi- 

 tion of the cow at the time of milking will greatly 

 influence the secretion of milk. 



As previously stated, there are many theories 

 advanced as to the formation of milk. It was 

 formerly claimed by some that milk is filtered 

 out of the blood; the udder being well supplied 

 with arteries and veins probably giving rise to 

 this idea. 



We find, however, that there is very little if 

 any milk sugar in the blood, while there is a 

 great deal in milk. No casein is found in the 

 blood. It is also a fact that the albumen in milk 

 coagulates differently from the albumen of the 

 blood. Further, it is known that the ash in milk 

 is not the same as the ash in the blood. It is 

 believed that somehow in the process of secretion 

 certain parts of the blood enter the cavity of the 

 alveoli cells and that there certain changes take 

 place, which result in the secretion of milk. 

 While the process of secretion is going on, new 

 epithelial cells are constantly being formed, but 

 just how is not known at the present time. 



Composition cannot be changed by feeding. 

 The attention of the reader is now called to a 

 very important point, viz.: that the tendency of 

 the cell is always to produce milk of its own par- 

 ticular composition. This tendency is very con- 

 stant, and therefore the composition of milk can- 



