EFFECTS ON THE VISUAL APPARATUS 



217 



corresponds to human keratomalacia, and belongs in the category of diseases 

 due to partial inanition, such as scurvy and beriberi. 



Some of the changes in the eyes of rats with experimental xerophthalmia are 

 shown in Figs. 68 and 69. 



Fig. 68. — Photograph of two albino rats of the same litter, placed at 3 weeks of age on a 

 diet deficient in vitamin A (patent wheat flour, 66 per cent; "Crisco," 20 per cent; casein, 

 5 per cent; yeast, 5 per cent; plaster of Paris, 2 per cent; sodium chloride, 2 per cent). In 

 about a month, both developed xerophthalmia. This is shown in rat "A," with perforated 

 cornea and protruding lens in the right eye. Rat "B" had a similar ophthalmia, without 

 corneal perforation, but recovered perfectly (as shown in the photograph) in 6 days after the 

 addition of dried spinach to the diet. (Courtesy of Professor McClendon and Miss Schuck.) 





Fig. 69. — Sections illustrating the corneal changes in xerophthalmia produced in the rat by 

 a diet deficient in vitamin A. A, normal cornea. B, stage showing moderate changes: 

 proliferation of surface epithelium, with numerous mitoses; substantia propria invaded by 

 blood vessels and round cell infiltration, with occasional fibroblasts; Bowman's membrane 

 absent. /, surface epithelium; II, Bowman's membrane; III, substantia propria; IV, Desce- 

 met's membrane; V, posterior endothelium. (After Wason '21.) 



McCollum and Simmonds ('18) (also Jour. Biol. Chem., 1917, 3 2:iSl ) 

 described the condition in young rats resulting from lack of vitamin A as a type 



