EFFECT ON ANIMALS AND MAN 



days prior to and for fourteen days during injection of vitamin B^g/^ 

 supporting the hypothesis that vitamin B^g makes folic acid available 

 to the organism ; when the Aminopterin was discontinued, a second 

 reticulocyte response was obtained. Four patients with untreated 

 pernicious anaemia excreted in the faeces a factor that stimulated 

 L. lactis in an amount equivalent to 0-3 to i-8 /xg. per g. of vitamin 

 B12, an amount in excess of that required to cure pernicious anaemia. 

 This was presumably produced by bacterial synthesis in the intestine. 

 That vitamin B^g has other functions than that of stimulating 

 haemopoiesis is perhaps the conclusion to be drawn from the observa- 

 tions of Wetzel et al.,^^ who tested the effect of the vitamin on a group 

 of eleven children in " varying states of recovery from simple growth 

 failure ". Five were said to respond dramatically with increased 

 physical vigour, alertness, better general behaviour and increase of 

 appetite. In a case of severe allergic bronchitis, the symptoms 

 vanished during the first week of treatment. These striking results 

 may be connected with the effect of vitamin B^g on the utilisation of 

 protein (see below). 



Effect on the Growth of Animals 



Gary et al.'^^ described a factor, factor X, the absence of which 

 resulted in a decline in the growth rate of rats, a decline that became 

 more marked the higher the protein content of the diet. This factor 

 appeared to be similar to the so-called animal protein factor (APF), 

 which increased the hatchability of hens' eggs ^^ and the growth rate 

 of chicks maintained on an all- vegetable protein ration,^ ^ and to a 

 factor in cow manure that stimulated the growth of chicks.^^' ^^ 



Crystalline vitamin B^g was found to exhibit animal protein factor 

 activity on chicks fed soya bean meal as the sole source of protein ; it 

 was as effective as the cow manure factor in stimulating the growth of 

 chicks.i^ It also increased the growth rate of rats on a factor X-de- 

 ficient diet, showing that vitamin B^g plays a fundamental role in the 

 utilisation of protein. ^^ In fact, evidence appears to be accumulating 

 that vitamin B12 is concerned with transmethylation. In the first 

 place, on a diet complete in the known vitamins, the growth of chicks 

 was improved by supplementation with choline or betaine ; the addi- 

 tion of a liver paste containing little choline was even more effective 

 and supplementation with choline or betaine then had little effect.^^ 

 Secondly, crystalline vitamin B^g increased the growth rate of chicks 

 on a diet low in choline, whilst renal injury in rats due to a low intake 

 of choline and methionine was minimised by the addition of vitamin 

 B12 to the diet, and the gain in weight was also increased, though not 

 when adequate amounts of choline were fed.^i Thirdly, vitamin B^g 



539 



