IV. BIOCHEMICAL SYSTEMS 



439 



the ground i)eas in the l)asal diet were extracted with hot alcohol, the 

 growth response to homocystine in the presence of vitamin B12 largely 

 disappeared, but it could he restored by adding choline to the diet as shown 

 in Table VIII. This leads to the conclusion that choline was an effective 

 methylating agent for homocystine under the conditions of these experi- 



TABLE VII 

 Weight of Chicks at 25 Days on Purified Diet 2 with Various Supplements; 



DiMETHYLAMINOETHANOL OmiTTED; PGA AdDED TO BasAL DiET 



Supplemental addition 



First addition per kilogram of diet 



None 



Homocystine 



V^itamin Bi2 



B12 + homocj^stine 



Methionine 



B12 + methionine 



TABLE VIII 

 Effect of Various Supplements on Perosis in Chicks on Diet 2 



Maximum poeaible score 



40. 



ments, and that glycine and serine, which were undoubtedly present in 

 substantial quantities in the basal diet, were relatively ineffective. 



2. In Rats 



The growth of rats in response to various sulfur amino acids was studied 

 by White and Beach. "^ They used a diet containing starch, hydrogenated 

 cottonseed oil, arachin, salt mixture, and cod liver oil. The rats received 

 daily supplements of 100 mg. of rice bran extract and 100 mg. of crude 



"1 A. White and E. F. Beach, J. Biol. Chem. 122, 219 (1937). 



