84 THE VITAMINS 



vitamin B through a bacterial symbiosis in the digestive tract. To test 

 this an artificial opening was made into the rumen of a cow which 

 had always received the vitamin B-poor food and the contents of the 

 rumen were tested for vitamin B by the usual feeding experiments on 

 rats (Bechdel, Honeywell et al., 1928). Weight for weight, the dried 

 residue of the bacteria isolated from the rumen appeared as rich in 

 vitamin B as dried yeast. That synthesis of vitamin B in the digestive 

 tract is a common occurrence is suggested by the finding of vitamin B 

 in the excreta. Salmon (1925) showed that the feces of rats may be 

 rich in vitamin B even when the diet is low in this factor, particularly 

 if through the presence of undigested food residues in the intestinal 

 tract the conditions are favorable for bacterial growth. It would thus 

 seem that cows and other ruminants are not unlike other species in 

 their vitamin B requirement, but that, through their peculiar digestive 

 apparatus, conditions are particularly favorable for the synthesis of 

 vitamin B by bacteria and for the utilization of the vitamin thus 

 synthesized. 



Fridericia and coworkers (1927) reported that young rats occa- 

 sionally recover spontaneously from the effect of vitamin B deficiency 

 and are able to live for months with no vitamin B in their diet and 

 even to transmit this immunity to their young. This phenomenon, which 

 has been named "refection," is said to be accompanied by a marked 

 change in the character of the feces which become white from un- 

 changed starch granules. The refection may be transmitted artificially 

 by feeding the white feces for a few days provided the diet contains 

 starch. The phenomenon has been confirmed by Roscoe (1927a) who 

 noted its spontaneous occurrence in some rats on a vitamin B-free diet 

 and was later able to transmit it to other rats by feeding the feces of 

 refected rats. Refection was also induced in rats on diets containing 

 either vitamin B or vitamin G but not on diets containing dextrin or 

 cooked instead of raw starch. These findings point to the synthesis of 

 vitamins B and G by bacterial processes in the intestinal tract under 

 conditions involving defective digestion of starch. 



Mendel and Vickery (1929) report that they have never encoun- 

 tered "refection" in their rats receiving a variety of uncooked starches. 



The extent of elaboration of vitamin B by bacteria depends on the 

 medium upon which the organisms are grown, however, as was shown 

 by the variations in the vitamin content of yeasts grown on beet 

 molasses, cane molasses and malt extract (Randoin and Lecoq, 1928). 

 So far as we know, the synthesis of vitamin B appears to be associated 

 only with the metabolism of plant life. 



