152 NUTRITIONAL PHYSIOLOGY 



will be inevitable and when the type-setting has to halt 

 there will be some unused letters. The shrinkage will be 

 much greater if the second page is to be printed in a lan- 

 guage other than the original. Suppose, for example, the 

 type used in English composition is next devoted to Ger- 

 man. The resulting difficulty is readily foreseen the 

 letter z is uncommon in English, but frequent in German. 

 Hardly a line can be perfectly set up before this -letter will 

 be vainly sought. Almost the whole collection of type will 

 be useless for composing. This is analogous to the attempt 

 to minister to animal growth with some isolated vegetable 

 protein of exceptional constitution. Offering the cleavage 

 products of gelatin to the cells is like giving the compositor 

 incomplete fonts of type. He cannot set up connected 

 matter if some of the letters are not to be found. 



It seems natural to assume that the closer the structural 

 resemblance between the proteins digested and those to be 

 synthesized, . the more economically the making over can 

 be accomplished. It is permissible to infer that nutri- 

 tion can be subserved by a smaller quantity of proteins 

 when they are derived from animal sources than when 

 they are of vegetable origin. One cannot, however, use 

 this as a strong argument against vegetarianism. The 

 quantity of proteins which one takes when following the 

 dictates of the appetite is apparently so liberal that all 

 constructive requirements are easily met, even though the 

 difference between the composition of the food-proteins 

 and those of the body is a wide one. Too rigorous logic 

 applied in this connection might lead to the recommending 

 of cannibalism. 



Our knowledge of the place and the manner of protein 

 synthesis is incomplete. The cells which line the intestine 

 and receive the digestive products are generally held to 

 bear a large part in the work. The fact that these cells 

 contain erepsin, an enzyme capable of breaking down the 

 more complex nitrogenous bodies, does not exclude the 

 possibility that dehydrations and condensations may still 

 take place within them. The enzyme may be modified un- 



