(1 1:2 METABOLISM 



the glycocoll and which to the tryptophane groups, can not as yet 



be definitely stated. The investigation of this problem has to be under- 

 taken by experiments of an entirely different type — namely, by observing 

 the welfare and growth of animals fed on proteins of varying amino- 

 acid composition. A full discussion of these experiments is given in 

 the chapters on Nutrition and Growth. 



