76 THE VITAMINS 



B, and desiccated pituitary gland (whole gland and anterior lobe), 

 thyroid, thymus, testicles and ovarian tissues were also found to be 

 deficient in this vitamin. 



The only apparent deviation from the normal noted in the nitrogen 

 metabolism of rats on diets deficient in vitamin B was the appearance 

 of creatinuria accompanied by a slow wasting of the skeletal muscles. 

 Drummond was unable to determine the cause of the fatal decline 

 which invariably follows such deficiency. Symptoms of nerve disorder 

 were found in only three of the many cases studied. 



Osborne and Mendel had suggested, in their earlier studies of vita- 

 min B, a quantitative relationship between vitamin B requirements 

 and growth. Definite proof that the requirement is somewhat pro- 

 portional to the amount of active tissue was afforded by the re- 

 sults obtained in a long continued study (Osborne and Mendel, 1922b) 

 of the growth of rats of different ages on varying amounts of yeast 

 as the sole source of vitamin B. Groups of rats weighing 40, 70, 

 150 and 240 grams, not less than five rats in each group, were fed 

 the basal diet with the addition of 25, 50, 100 or 200 milligrams 

 daily of yeast, each amount of yeast being fed to a group of each initial 

 weight. 



In the four groups receiving 200 milligrams of dried yeast daily, 

 the animals, with few exceptions, reached the average adult size within 

 the average time. With 100 milligrams, the results were less satisfac- 

 tory, particularly after the animals reached a weight of 200 grams. 

 With the smaller doses, 50 and 25 milligrams, the rate of growth was 

 more or less retarded from the very beginning of the experiment, and 

 in the case of the larger animals 25 milHgrams failed to secure even 

 maintenance of body weight. 



On recalculating the various dosages to the amount in milligrams 

 per 100 grams of body weight, the daily requirement appeared to have 

 a quantitative relationship to the mass of active tissue and to approxi- 

 mate from 50 to 60 milligrams of the dried yeast daily. The observa- 

 tion that a number of the larger animals appeared to require a smaller 

 amount of the vitamin per unit of body weight was explained on the 

 ground that these animals were comparatively rich in fat and the actual 

 amount of active tissue was smaller than the weights would indicate. 

 Another illustration of the dependence of the rate of growth upon the 

 vitamin dosage was afforded by the growth curves of six rats from 

 the same litter, each of which was put, when it reached a weight of 

 100 grams, on the standard diet, but with differing amounts of yeast. 

 With decreasing amounts of yeast the growth was about the same for 



