Is there More than One Kind of Rickets? 153 



III. Discussion. 



Our experiments make it clear that in the rat, when deprived 

 of certain active light rays and an unidentified factor contained 

 in cod liver oil, a pathological condition corresponding in all 

 fundamental respects to the rickets of the human being can be 

 produced through the diet in two ways; it can be produced (1) 

 by diminishing the phosphorus in the diet and supplying calcium 

 in excess of the optimal or at the optimal concentration, or (2) by 

 reducing the calcium but maintaining the phosphorus at a con- 

 centration somewhere near the optimal. In the former case the 

 calcium-phosphate ratio in the diet is large, in the latter case it is 

 small. We have not the slightest doubt that in the human being 

 similarly deprived of active light and the unidentified factor it 

 would be possible to produce true rickets through a manipulation 

 of the calcium and phosphorus of the diet in the two ways men- 

 tioned. As the result of our experiments we are led to believe, 

 therefore, that there are two main forms of rickets, one character- 

 ized by a normal or nearly normal blood calcium and a low phos- 

 phorus, the calcium-phosphate ratio being high, the other by a 

 normal or nearly normal blood phosphorus but a low calcium, the 

 calcium-phosphate ratio being low. Between the two forms there 

 are probably innumerable intermediary forms marked by calcium- 

 phosphate ratios which are less effective in preventing calcium- 

 phosphate deposition. Diets with these intermediary ratios 

 manifest themselves pathologically as rickets in various stages of 

 healing or of healing and relapse or as slight disturbances of 

 calcification of the skeleton which have more or less remote 

 resemblance to rickets. 



At one time we were under the impression that tetany sharply 

 marked off one form from the other, i.e., that the two main divi- 

 sions of rickets were ordinary rickets and the rickets of tetany. 

 The investigations of Howland and Kramer 1 have shown, however, 

 that tetany in a latent form, at least, may be associated with the 

 low phosphorus form of the disease. Though tetany may occur 

 with the low phosphorus form, however, it is probably regularly 

 associated with the low calcium form and may be regarded as a 



1 Howland, John, and Kramer, Benjamin. Amer. Jour, of Dis. of Child., 1921, 

 xxii, 105. 



