THE PROTEINS AND THEIR METABOLISM 129 



TABLE X 

 RAT 1773 



RAT 1900 



point of 150 grams on October 14. It will be noticed in this experiment 

 that on zein plus tryptophan the loss in weight was not as marked as on 

 zein alone (rat 710). In many other experiments, Osborne and Mendel 

 found that on zein and tryptophan the animals were able to maintain their 

 body weight, but in no instance was an animal able to grow until after 

 lysin was added. This led them to differentiate between maintenance 

 and growth in nutrition. Without tryptophan, they showed, all animals 



