VITAMIN D 325 



that either 20 per cent wheat embryo, or 50 per cent hog millet may be 

 used to supply vitamin A without an appreciable amount of vitamin D, 

 as shown both by the effects upon growth and the degree of calcification, 

 when none or an ample supply of vitamin D was added to the basal diet. 



McCann and Barnett (1922) studied the distribution of phosphorus 

 and calcium between the skeleton and soft parts of rats on rachitic and 

 non-rachitic diets, and Chick, Korenchevsky and Roscoe (1926) com- 

 pared the chemical composition of the skeletons of young rats fed (1) 

 on diets deprived of fat-soluble vitamins, and (2) on low-phosphorus 

 rachitic diets with those of normally nourished rats. 



Sherman and Hessler (1927) used the percentage of calcium in the 

 total body as a means of judging the influence of the antirachitic factor 

 upon calcification. 



Sherman and Stiebeling (1929) studied quantitatively the responses 

 in growth and degree of calcification made by young rats to graded 

 allowances of vitamin D at different periods during the first several 

 months of life. They found, in young rats reared by mothers on a diet 

 consisting essentially of two-thirds ground whole wheat and one-third 

 whole milk powder and transferred at the twenty-first or twenty-eighth 

 days of age to a basal diet decidedly deficient in vitamin D but other- 

 wise adequate (calcium, 0.74 per cent; phosphorus, 0.58 per cent), 

 that practically normal calcification resulted at the fifty-sixth day of 

 age in cases in which the basal diet was supplemented by whole 

 (summer) milk powder to the extent of about 5 per cent of the calories ; 

 at the eightieth day of age in cases in which the basal diet was supple- 

 mented during the preceding 4 weeks by whole milk powder to the 

 extent of 8 to 9 per cent of the calories ; and at 150 and 180 days of age 

 in cases in which the basal diet was supplemented during the preceding 

 8 weeks by whole milk to 4 to 5 per cent of the calories. Feeding smaller 

 graded portions of the milk as source of vitamin D resulted in corre- 

 sponding improvements in calcification over their respective negative 

 control. In all these cases, the vitamin D was the sole significant vari- 

 able, the calcium and phosphorus content of the food as a whole being 

 kept constant. They found it possible to make satisfactory comparisons 

 only when the groups of test animals are controlled by two other 

 groups, containing representatives from the same litters and matched 

 in sex and weight, the one receiving no added vitamin D, the other an 

 ample supply. They suggested that, at whatever age the studies on rats 

 are terminated, quantitative comparisons of the vitamin D content of 

 materials under investigation be made at that level of intake which will 

 induce a degree of calcification midway between the minimum and 



