VITAMINES 35 



offer facts whicli make a bridge to the case of human 

 nutrition. 



The striking thing, the point that we are now 

 concerned with, is the extremely small amount of 

 material which as an addendum will — if rightly 

 chosen — convert these wholly inefficient artificial 

 diets into efficient ones. In some early experi- 

 ments of my own, for example, the addendum was 

 a minute amount of milk. The amount of solid 

 matter contained in this added milk represented 

 at most three or four per cent of the whole food 

 eaten by the animals, and as most of the constituents 

 supplied in it were already in the diet any special 

 substance must have formed a very small proportion 

 indeed of the whole supply of food. Yet, without 

 this small addendum young animals did not grow : 

 with it they grew satisfactorily. With it they lived ; 

 without it they ultimately died. Similar results 

 are got by the addition of equally small amounts 

 of other materials ; but they must be preparations 

 made from plant or animal tissues. They must 

 contain something made originally by living cells. 

 All our natural foods are parts of tissues which have 

 lived. We ultimately owe our supply of them to 

 the plant, and the plant evidently makes and stores 

 certain substances in very small quantity, which 

 are, as experiment proves, as important to the 

 animal and to the human body as the proteins and 

 the starch which it makes in so much larger quantity. 



