194 



Scientific Proceedings (114). 



In continuing by means of feeding experiments upon rats 

 the study of the mineral elements in nutrition which has engaged 

 much of the attention of one of us for the past fifteen years, we 

 have found a relatively simple diet which has led to the develop- 

 ment of rickets in every one of the cases thus far examined ; while 

 complete protection was afforded by the addition of 0.4 per cent, 

 of potassium phosphate (K 2 HP0 4 ) to this diet, or (more strictly) 

 by the introduction of this mount of potassium phosphate in 

 place of a part of the calcium lactate which the rickets-producing 

 diet contained. 



In our experience healthy rats of families on normal diet when 

 separated from their mothers at 28 to 30 days of age average 

 about 40 grams in weight and a calcium content of about 0.3 gram 

 or 0.7 per cent. If then placed upon good diet the calcium content 

 of the body increases in greater ratio than the body weight so 

 that the percentage of calcium in the body rises continuously 

 until at about four to six months of age the adult percentage of 

 calcium — about 1 to 1.25 per cent, of the body weight — is reached, 

 after which the weight of the body and the weight of calcium which 

 it contains continues parallel until growth is complete. 



If, however, the healthy young rat after weaning is placed 

 at the age of 28 to 30 days upon a diet consisting of patent flour 

 and sodium chloride, growth in body weight is practically sus- 

 pended and simultaneously the body practically ceases to increase 

 its calcium content. In such case the rat usually lives about six 

 weeks upon the experimental diet with hardly any change either 

 in body weight or total body calcium. Such rats showed multiple 

 fractures, marked deformity of the thorax, and osteoporosis. 



In parallel experiments in which calcium lactate, with or 

 without ferric citrate, was added to the diet of patent flour and 

 sodium chloride (Diets 83 and 84), there was little or no growth 

 in body weight but the body gained sufficient calcium so that its 

 percentage of calcium after 4 to 6 weeks on this diet was about 

 the same as in a normal rat of the same age, though the absolute 

 amount of calcium contained in the body was much below that 

 of a normal rat of the same age, as would be expected in view of 

 the suspension of growth. These rats uniformly showed rickets. 



When with all other conditions the same, the diet was modified 



