BIOLOGICAL CLASSIFICATION OF FOODS 53 



supply this dietary factor (fat-soluble A) in the food of children 

 except in the form of milk-fat, and milk is therefore an indis- 

 pensable food for the young." 



Attention should be called to one other point. It has been 

 suggested by some that possibly pasteurization of milk or cream 

 destroys the growth-promoting qualities of the " fat-soluble A " 

 in the fat. Osbourne and Mendel found that passing live steam 

 through milk-fat for two hours did not affect it, and McCollum 

 and Davis found that it was not affected by being heated to 

 the boiling-point of water. This should be satisfactory evidence 

 that pasteurization of milk or cream in no way affects the growth- 

 promoting qualities of the milk-fat. 



