4 6 



Scientific Proceedings (117). 



The rats exposed to the sunlight, on the other hand, showed 

 none of the evidences of rickets. The thorax was not deformed; 

 the costochondral junctions were normal. There were no frac- 

 tures of the ribs. The ends of the long bones were not enlarged. 

 The long bones cut with great resistance. On microscopic ex- 

 amination the cartilage was normal. The proliferative zone was 

 completely calcified. The trabecular were completely calcified. 

 The condition found was normal except that both microscopically 

 and grossly the bone was more delicate than in the rat of corre- 

 sponding age reared on satisfactory diets. Though the sunshine 

 completely prevented the development of rickets, it did not entirely 

 compensate for the deficiency of phosphorus in the diet, either as 

 regards the growth and development of the rat as a whole or of the 

 skeleton. 



There were some noteworthy findings outside the skeleton. An 

 abundance of fat was present. In the control rats the fat was 

 scant. The thymus was only partially involuted. In the control 

 rats it was completely involuted. The spleen was not enlarged. 



Discussion. 



Sunlight effectually prevents the development of rickets in the 

 rat. We have already shown, 1 as has also Pappenheimer, that 

 cod-liver oil prevents the development of rickets in the rat. As 

 nearly as we can judge from the radiographs furnished by Huld- 

 schinsky and others the mode of healing at the cartilage-shaft 

 junction induced by the ultraviolet ray (sunlight) is exactly 

 analogous to that which occurs after the administration of cod- 

 liver oil, as determined by Howland and Park. 2 The time rela- 

 tions are also similar. Huldschinsky found that the ultraviolet 

 ray produced definite evidences of healing at the end of four weeks, 

 and at the end of two months almost complete healing. Howland 

 and Park found that cod-liver oil first gave rise to evidences of 

 healing at the junctions, of the cartilage and shaft of the long bones 

 three weeks after the administration was begun and that at the 

 end of about two months the calcification of the diseased ends of 



Shipley, P. G., Park, E. A., McCollum, E. V., and Simmonds, Nina. Proc. 

 Soc. Exper. Biol, and Med., xviii, 227, 1921. 



2 Howland, J., and Park, E. A., Arch. Pediat., 1920, xvxvii, 411. 



Howland, J., and Park, E. A., Bull. Johns Hopkins Hosp., November, 1921. (To 

 be published.) 



