Figures 104 to 110 are photomicrographs of the rat retina (X 400) aiul are 

 reproduced from an article by Johnson, 1939, ,/. Exp. Zool., vol. 81. See 

 below for separate captions. 



Fig. 104. Section through the fundus of a normal, dark-adapted retina. 



Fig. 105. Section from central portion of the fundus of the retina shown in 

 figure 109. The visual cells, the outer nuclear layer, the outer molecular layer, 

 and most of the inner nuclear layer have completely degenerated and have been 

 replaced by connective tissue. The epithelial pigment layer is entirely absent 

 and the choriocapillaris is firmly joined to the retina by connective tissue (cf, 

 figure 104). 



Fig. 106. Photomicrograph of a section of the retina (fundus) from rat 

 which had been fed adequately for 10 days following severe vitamin A-defi- 

 ciency. 



Fig. 107. Section through the fundus of the retina from a rat with symp- 

 toms of moderate vitamin A-deficiency. A) The few remaining rod outer seg- 

 ments (O.S.) are broken off at the junction with the inner segments. B) The 

 outer segments are entirely gone, and the inner segments (I) are degenerating. 

 The external limiting membrane is not discernible (cf. figure 104). 



Fig. 108. Section through the periphery of the retina from a rat suffering 

 from severe vitamin A-deficiency. The rod outer segments are gone, the inner 

 segments (I.S.) are degenerating, the external limiting membrane is not dis- 

 cernible, and the outer rows of visual cell nuclei are degenerating. 



Fig. 109. Section through the periphery of the retina from a rat suffering 

 from severe vitamin A-deficiency. In the region A, a few rod inner segments 

 remain, the external limiting membrane is gone and the outer nuclear layer has 

 begun to degenerate. In region B, the visual cell layer is entirely gone and the 

 remaining visual cell nuclei are pyknotic or karyorrhectic. 



Fig. 110. Section from the retina (fundus) of a rat suffering from severe 

 vitamin A-deficiency, showing rosette ""formation. The deformity involves 

 only the visual cell layer and the outer nuclear layer. 



155 



