2 3 8 



Scientific Proceedings (121). 



In view of this experiment another series of rats were put on the 

 same diet (Sherman and Pappenheimer plus 25 mg. P. per cent., 

 in the form of secondary potassium phosphate). This addition 

 furnishes a level of phosphorus which is still inadequate for the 

 rat, and leads to rickets. Of the four receiving this diet all showed 

 signs of rickets according to x-ray after 32 days. After 48 days, 

 however, the radiographs showed healing. During this period 

 the rats had made a total gain of 92 g. After 74 days the x-ray 

 showed the lesions apparently healed, and the rats were killed. 

 No gross evidences of rickets were found at necropsy. Micro- 

 scopic examination of the costo-chondral junctions also showed no 

 evidences of active rickets; the rickets was either healing or there 

 was merely osteoporosis. 



The explanation suggested for this spontaneous healing is that, 

 with a practically stationary weight over a long period, the 

 phosphorus requirement for the building up of new tissue is greatly 

 reduced. The small addition of P. under such circumstances, 

 to the standard rickets-producing diet, suffices to enable the bone 

 to recalcify. 



104 (1851) 



A further report on the prevention of rickets in rats by light rays. 

 By ALFRED F. HESS, LESTER J. UNGER, and A. M. PAPPENHEIMER. 



[From the Department of Pathology, College of Physicians and 

 Surgeons, New York City.] 



In a previous communication we showed that the development 

 of rickets in rats fed the standard rickets-producing diet of Sher- 

 man and Pappenheimer can be prevented by daily exposures to 

 direct sunlight for fifteen minutes. 1 A similar result has been 

 reported by others. 2 If the rats are placed in a box having flint 

 glass windows, it was found that the sun's rays which had traversed 

 the glass had lost their protective power. Rays which were re- 

 flected to the rats from a white surface retained some of their 



1 Hess, A. F., Unger, L. J. f Pappenheimer, A. W., Proc. Soc. Exp. Biol, and 

 Med., 1921, xix, 8. 



'Shipley, P. G., Park, E. A., Powers, G. F., McCollum. E. V., Proc. Soc- 

 Exp. Biol, and Med., 1921, xix, 43. 



