Rickets in Rats 



371 



179 (2139) 



The influence of nutrition during the pre-experimental period on 

 the development of rickets in rats. 



By ALFRED F. HESS, M. WEINSTOCK and E. TOLSTOI. 



[From the Department of Pathology, College of Physicians and 

 Surgeons, New York City.] 



Whether or not rickets develops on standard "rickets-pro- 

 ducing' dietaries may depend on the stock of rats which is used. 

 In our experiments rats from six different sources were tested. 

 It was found that four of these stocks regularly developed 

 rickets when fed from the age of four to eight weeks on the 

 Sherman-Pappenheimer diet; one stock developed rickets but 

 showed a definite tendency to spontaneous calcification of the 

 bones, and one absolutely failed to develop rickets. This re- 

 fractory group comprised 50 rats four weeks of age. They 

 failed to develop rickets either on the low phosphorus and high 

 calcium diet (No. 84) or on the low calcium and high phos- 

 phorus diet (No. 85 C). On the dietary employed by McCollum 

 and his associates, which contains 3 per cent, of calcium car- 

 bonate, rachitic lesions developed in some animals but not in 

 others. It is evident, therefore, that the term "rickets-producing 

 dietary" cannot be applied unreservedly but rather in relation to 

 definite stocks of animals. 



The divergence in susceptibility is, to some extent, associated 

 with a variability in the percentage of inorganic phosphate of 

 the blood. There is, however, no strict parallelism in this re- 

 spect. The blood of rats four weeks of age has been found to 

 vary in this constituent from 6.5 mg. to 12.0 mg. per cent. ; the 

 calcium has ranged from 6.1 mg. to 8.2 mg. per cent.. The re- 

 fractory rats had the highest percentage of inorganic phosphate 

 in the blood. 



The resistance of this stock is not to be attributed mainly to 

 peculiarity of strain or breed but to previous diet, for it was over- 

 come by modification of the dietary. Pregnant rats of this strain 

 were obtained and fed the stock laboratory dietary as soon as 

 they had given birth to young and throughout the lactating 

 period. At the end of four weeks the young were placed on the 



