THE RETINA. 



37 



When examined during life by the aid of the ophthalmoscope, the optic disc appears 

 of a light grey tint, contrasting strongly with the red colour of the rest of the field. In 

 the central depression of the disc are remnants of the tissue which, iu the foetus, accom- 



nasal 



temporal 



FIG. 46. VIEWS OF THE POSTERIOR PART OF THK RETINA. Variously magnified. 



A. The posterior half of the retina of the left eye, viewed from before. (Henle.) Twice the 

 natural size. 



s, cut edge of the sclerotic ; ch, choroid ; r, retina : in the interior at the middle the macula lutea 

 with the depression of the fovea centralis is represented by a slight oval shade ; towards the left side 

 the light spot indicates the colliculus or eminence at the entrance of the optic nerve, from the centre 

 of which the arteria centralis is seen sending its branches into the retina, leaving the part occupied by 

 the macula comparatively free. 



B. Fundus of the eye, as seen with the ophthalmoscope. (Jaeger.) Somewhat magnified, 

 n, a, arteries ; v, v, veins ; /, fovea. 



C. The point of entrance of the optic nerve as seen with the ophthalmoscope. (Jaeger.) Magnified 

 still more. 



A, optic nerve, passing through the lamina cribrosa, L, which shows through the disc-like expansion 

 of the entering nerve ; a, ring of connective tissue ; b, choroidal ring ; c, branches of the central artery 

 of the retina, y ; d, branches of the central vein, // ; n, inner or nasal side ; t, outer or temporal side. 



