The Prevention of Rickets in Rats. ii 



A. Darkness. 





Duration 







Microscopic 



uiet. 



(ua.ys). 



■R of TvTn 

 XV c± L IN (J. 



X-Ray. 



XZsAdliXlllcl- 











tion. 





34 



24O 



T> 

 XV. 



"D 



Xv. 





23 



247 









22 



248 



— 



R. 





— 



436 



R. 



— 







All 



R. 







3° 





R. 



R. 





39 



262 



R. 



R. 





39 



263 



R. 



R. 





39 



264 



R. 



R. 





28 



443 



R. 







28 



444 



R. 



R. (slight) 





28 



445 



R. 





No. 84 + 75 mg. P 



38 



121 



neg. 



neg. 





38 



122 



neg. 



neg. 





38 



123 



neg. 



neg. 



B. Sunlight. 





Duration 







Microscopic 



Diet. 



(Days). 



Rat No. 



X-Ray. 



Examina- 











tion. 



No. 84 



34 



249 



neg. 



neg. 





32 



250 









35 



251 









33 



439 









33 



440 









33 



441 









33 



442 







No. 84 -f- 25 mg. P 



39 



259 









39 



260 









39 



261 







No. 84 + 75 mg. P 



38 



124 









38 



125 







R. = rickets. 











light. The most interesting aspect of the question, however, is the 

 phenomenon that the sun's rays are able to stimulate a deposition 

 of inorganic salts where these are lacking. The damaging effect 

 of darkness emphasizes the fact that sunlight is of great impor- 



1 Diet No. 84 as originally constituted, contained 86 mg. per cent, of phos- 

 phorus. In the fall, however, owing to a variation in the phosphorus content of 

 the flour, this diet was found by analysis to contain only 72 mg. per cent. Rats 

 numbered our 400 (in this table) were fed on the ration having the lower phos- 

 phorus content. 



