516 



VITAMIN Bi2 



that oysters were an even better source than hver. The richest natural 

 source encountered was the eggs of the crustacean Artemia salina which 

 had activity equivalent to 7.2 7 of vitamin B12 per gram of solids by assay 

 with rats. 

 Emerson- studied the effects of vitamin B12 by the oral and subcutaneous 



TABLE XXII 

 Comparison of Effects of Vitamin B12 and Liver Extract on Growth^^ 



Sets of 



Casein litter- Duration 



level, mate of assay, 



% male rats days 



Negative 

 control 

 average 

 gain in 



weight, g. 



Vitamin B12 (cryst.) 



Daily 

 dose, 7 



Average 



gain in 



weight, g. 



IS-unit liver extract 



Average 

 Daily gain in 



dose, ml. weight, g. 



The basal diet consisted of casein, extracted ten times with hot alcohol, dried yeast (10% of diet) 

 dextrin, lactose, minerals, and vitamins without B12). 



TABLE XXIII 



Effect of Vitamin B12 on Growth of Male Rats Receiving a Diet Containing 



60% Soybean Meal and 0.25% Thyroid Powder. Average Weight 



at Start of Test Period: 120 G.^^ 



Supplement, daily 



Gain in weight, 15 day s 



None 



0.5 7 vitamin B12, orally 



0.5 7 vitamin B12, subcutaneously 



0.25 7 vitamin B12, orally 



0.25 7 vitamin B12, subcutaneously 



0.125 7 vitamin B12, orally 



0.125 7 vitamin B12, subcutaneously 



0.0625 7 vitamin B12, orally 



0.0625 7 vitamin B12, subcutaneously 



28 

 79 

 74 

 72 

 73 

 65 

 71 

 51 

 50 



routes in rats fed a diet high in soybean meal and containing 0.25 % of 

 thyroid powder, U.S.P. Male rats averaging 40 g. in weight were placed 

 at weaning on the basal diet for a depletion period of 28 days following 

 which they were giv^en the supplements shown in Table XXIII for 15 days. 

 The results indicated that vitamin Bi2 was utilized equally well either orally 

 or subcutaneously and that the requirement was almost satisfied by 0.125 

 7 daily for a rat averaging about 150 g. in weight during the course of the 

 experiment. This places the requirement at about 0.8 y per kilogram of body 

 weight per day. This is markedly in excess of the requirement of a human 



