in] 7^ CONSTITUENTS O 



of the milk. If, however, in addition to ether, a 

 potash or soda solution be added, the ether speedily 

 dissolves the fat, and the milk becomes much clarified. 

 According to the supporters of the membrane theory, 

 the alkaline solution dissolves the membrane and 

 permits the ether to act upon the fat. That this, 

 however, is not the true explanation has been 

 strikingly proved by Soxhlet, who found that milk 

 to which potash or soda solution had been added is 

 not clarified by the addition of benzene or chloro- 

 form equally powerful fat solvents. It seems clear 

 that the peculiar action of ether is due to another 

 cause, which need not here be discussed. Lastly, 

 the liquid state of the fat in the globules may be 

 explained as due simply to their isolation, and 

 furnishes an example of what is chemically known 

 as superfusion. It is a well-known fact that any 

 liquid, if it is in a sufficiently fine state of division, 

 may be cooled down below its freezing-point without 

 becoming, frozen. A sudden impact, however, will 

 convert it into the frozen state. 



If, then, it may be said that the fatty globules have 

 an envelope, it can amount to nothing more than a 

 mere liquid envelope, such as the film of a soap- 

 bubble. 



Chemical Composition of Milk- Fat. Milk -fat 

 differs from all other known kinds of fat in its 

 complex and highly characteristic chemical com- 



