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Scientific Proceedings (116). 



phosphate for an equal percentage of calcium lactate in this diet 

 (No. 84), uniformly protected against the development of rickets. 



These experiments have been continued. The diet has been 

 modified in various ways, and we wish this evening to report 

 very briefly some of the results obtained. 



The basic rickets-producing diet has been tested on a further 

 series of rats, amongst them controls for other experiments. In- 

 cluding the 15 rats referred to in the previous paper, 36 rats in all 

 have been observed to develop rickets upon Diet 84. A few of 

 these after having shown unmistakable rachitic changes by x-ray, 

 were subsequently given other diets. In all the other rats, the 

 diagnosis has been confirmed by microscopic examination. It 

 may be confidently stated then that rickets will develop in 100 per 

 cent, of animals upon this diet; at least, in our experience, there 

 have been no exceptions. 



The protective action of the basic potassium phosphate has 

 also been demonstrated in 9 additional rats; and there have been 

 no failures amongst the total 24 rats, which have been studied up 

 to date. 



The first question to be answered was as to the part played by 

 the potassium and the phosphate respectively, in the protection 

 afforded by the basic potassium phosphate. To determine this 

 point, an equivalent amount of primary sodium phosphate was 

 substituted for the potassium salt in the diet; and in another 

 series of the same litter, an equivalent amount of potassium 

 chloride for the potassium phosphate. The results of this ex- 

 periment are shown in Table II, from which it is apparent that 

 the protection is conferred by the phosphate, and not by the 

 potassium. 



Experiments to determine the minimal amount of phosphate 

 (calculated as P), which, when added to the basic diet 84 will afford 

 complete protection, are not yet completed. The data given, 

 however, indicate that this limit lies between 50 and 25 mg. per 

 cent., the original diet 85, containing 72 mg. of added phosphorus 

 per 100 gms. of diet, in addition to the 87 mg. contained in the 

 basic diet 84. 



As was pointed out in the previous paper, Diet 84 is inadequate 

 for proper growth, being deficient not only as to the character of 



