156 



THE AMINO ACIDS 



Days 



FIGURE 12. INDISPENSABILITY OF TRYPTOPHANE FOR MAIN- 

 TENANCE IN NUTRITION. These experiments should be contrasted 

 with the failure of maintenance on zein-food alone, shown in figure 

 11 . [From the Journal of Biological Chemistry ', volume 17 . ] 



phane and lysine results in the establishment of perfect 

 maintenance and growth. [See Fig. 13.] It may be 

 inferred from these experiments then that tryptophane 

 is indispensable for maintenance in nutrition and that 

 the animal organism does not possess the ability to 

 synthesize this amino acid. That lysine cannot replace 

 tryptophane in the establishment of the condition of 



