124 



A. I. RINGER 



. II 



DOG WAS FED 18 GRAMS OF PBEDIGESTED CASEIN. EXPERIMENT PROVES THAT NITROGENOUS 

 EQUILIBRIUM AND BODY WEIGHT CAN BE MAINTAINED ON IT 



III 



DOG WAS FED 22 GRAMS OF PREDIGESTED CASEIN, MINUS TRYTOPHAN. EXPERIMENT PROVES 

 THAT ANIMAL LOSES ITS OWN NITROGEN BY BEING IN NEGATIVE NITROGEN BALANCE, 

 AND ALSO LOSES IN BODY WEIGHT 



IV 



DOG WAS FED 20 GRAMS OF PREDIGESTED CASEIN PLUS TRYPTOPHAN. EXPERIMENT SHOWS 

 THAT NITROGENOUS EQUILIBRIUM WAS REACHED ON THE FOURTH DAY. ANIMAL GAINED 

 IN WEIGHT PROVING THAT TRYPTOPHAN IS AN ESSENTIAL AMINO ACID 



