196 



Scientific Proceedings (114). 



It is seen from the Table that rachitic lesions developed in 15 

 rats maintained on Diets No. 83 or No. 84 for a period varying 

 from one to two months after weaning. The rats surviving the 

 longer period, naturally, showed more extreme changes, but the 

 lesions were easily recognizable in the X-ray and in the gross 

 changes at the chondro-costal junctions, after four weeks. Nine 

 rats maintained for similar periods on Diet No. 85, which differs 

 from Diet 84 only in the substitution of 0.4 per cent. K 2 HP0 4 for 

 an equivalent amount of calcium lactate, showed entirely normal 

 bones, both grossly and micioscopically ; and six other rats, 

 five of which were changed to Diet 85 at the age of 60 days and 

 one at 81 days, also failed to develop rickets. 



While our work was in progress there have appeared the first 

 two of a series of papers by McCollum and his associates dealing 

 with the experimental production of rickets in rats by means of a 

 wide variety of deficient diets. In the first of these papers 

 McCollum and his co-workers state (p. 340) that they "are not 

 willing to hazard any statements in regard to the factors operating 

 to produce rickets in the child or the experimental animal"; 

 while in the second paper, published simultaneously, the same 

 authors say (p. 344) that by the use of faulty diets "especially 

 certain diets deficient in the socalled fat-soluble A or in both that 

 substance and calcium, the cartilage and adjacent portions of the 

 metaphysis of the long bones of the extremities could be rendered 

 entirely free from calcium deposits and a condition identical with 

 the rickets of human beings be obtained." 



In view of the emphasis thus given by these investigators, as 

 well as by others, to deficiency of calcium or of fat-soluble vitamine 

 or both as causing rickets, it has seemed to us that we might aid 

 in the attack upon this puzzling disease by placing on record at 

 this time our observations upon the prevention of rickets when 

 caused by the particular experimental diet here described, by 

 the simple Introduction of a single inorganic salt, and that not a 

 sail of calcium, into the diet . 



Without entering into detailed discussion of these results at 

 tin's time we desire to emphasize the following facts in order to 

 avoid misunderstanding. On the particular diel here used rickets 

 uniformly appeared in the absence, and was uniformly prevented 



