Development of Xerophthalmia in the Rat 83 



1, 1922, twelve young rats were placed on the doubly deficient 

 diet (3127); they were divided into four groups (each animal 

 in a separate cage). The first three groups were subjected to 

 the same conditions of light and darkness as heretofore described 

 in the report of the preliminary experiments; the fourth group 

 was exposed to direct sunlight. The daily period of exposure 

 to sunlight averaged four hours and to ultra violet radiation 

 thirty minutes. On April 20, 1922 a parallel experiment was 

 begun, using eighteen young rats and the diet producing xero- 

 phthalmia only (3392). 



Diet 3392 because of the inadequacy of its proteins both in 

 quantity and quality produces xerophthalmia in rats more quick- 

 ly than the doubly deficient diet 3127. 



The results of these experiments and the conclusions which 

 they warrant may be summarized as follows : 



On both diets the rats in the roomlight, darkness and violet 

 lamp groups developed xerophthalmia early, ceased to grow, be- 

 came markedly emaciated and died. On the doubly deficient 

 diet (3127) only the animals subjected to violet lamp radiation 

 and sunlight exposure failed to develop rickets. 



Radiation with the mercury vapor quartz lamp for thirty to 

 sixty minutes daily does not prevent the development of xero- 

 phthalmia but promotes bodily vigor to a very limited degree. 



The rats exposed to direct sunlight (with one exception) never 

 developed xerophthalmia until the animals in the other groups 

 had developed the disease and died. In some of these "sunlight" 

 rats xerophthalmia developed late and the animals died ; in others 

 the disease was manifested late also but in recurring mild at- 

 tacks ; in still others it occurred in a mild form from which there 

 was spontaneous recovery. Two of the rats never developed 

 xerophthalmia at all; one of these animals and one in which 

 there was spontaneous recovery were still living and free from 

 xerophthalmia when the experiment was terminated, five months 

 after it was begun. None of the animals had rickets. 



In the "sunlight" animals which developed xerophthalmia 

 and in all the rats in the other groups the disease was more 

 severe in the animals on diet 3392. 



The rats exposed to sunlight made an initial gain in weight 

 which in the animals on the rickets-xerophthalmia producing diet 



