66 



THE FUNDUS OCULI OF BIRDS 



A long, uniform band of two dark lines 

 enclosing a broader white band runs almost 

 horizontally across the fundus above the 

 optic disc. About the middle point of the 

 band (above the disc and towards the nasal 

 aspect of the fundus) is a round depression 

 (?), black in the center and surrounded by two 

 indistinct, pigmented semicircles, made by a 

 widening of the parallel lines that enclose the 

 fundal band. 



The extended major axis of the optic 

 entrance oval describes an angle of almost 

 45° with the inferior border of the retinal 

 band. 



This angle the writer has called the infula- 

 papillary angle, from infula, a band, and pa- 

 pilla, the optic disc. 



Plate I, page 121, gives a very good 

 idea of the ophthalmoscopic appearances in 

 this species. It represents the eyeground as 

 seen in specimens examined by Head in the 

 Gardens of the British Zoological Society and 

 by the writer in a young male adult living in 

 the open and under ideal conditions on the 

 Cawston Ostrich Farm near San Diego, Cali- 

 fornia. 



The general color of the eyeground is dull 

 red, varied by a uniform sprinkling of lighter 

 red, round dots and gray granules. The 

 lower half of the fundus appears somewhat 

 grayer in tone than the upper sectors. This 

 appearance is probably due to the numerous 

 opaque nerve-fibres that extend from all 

 sides of the papilla as a center across the fun- 

 dus to the periphery of the ocular background. 

 The red coloration of the fundus is seen to be 

 more intense towards the upper half of the 

 eyeground. The optic nerve-entrance is very 

 broad, oval in shape, and its contour resembles 

 that of Rhea and the Tinamous. The mar- 

 gins of the nerve-head are very white and it 

 is possible with the mirror to see all around 

 the pecten. The centre of the disc, including 

 the parts near the root of the pecten, is 

 stippled with minute, brown pigment dots, 

 like black pepper grains. 



The pecten proper rises from the nervehead 

 much like the same organ in the Tinamou, 

 and presents, ophthalmoscopically, the ap- 

 pearance of a number of dull, dark, sepia- 



brown tubercles. It does not project far 

 forward into the vitreous cavity, while its 

 outlines and contour may be distinguished 

 both above and below the disc. The pectin- 

 ate margins are formed of round or ovoid pro- 

 jections. These nodular masses also appear 

 to constitute the body of the pecten. 



The macula is situated about as it is in 

 Rhea; it is not very striking in appearance, 

 and takes the form of a crescentic arrange- 

 ment of minute, gray dots. It is seen towards 

 the nasal side of the disc near its upper end, 

 and is not surrounded by the closed reflex- 

 ring noticed in so many avian fundi. 



Rheiformes 



American Ostrich. Rhea americana. 

 For an exact reproduction in color of the 

 ocular background of this bird see Plate II, 

 page 121, which shows the left eye; erect 

 image. 



The coloration of the fundus as a whole is 

 buff, merging into dull red at the periphery. 

 It is stippled all over with minute dots of 

 a lighter tint, and much resembles the fun- 

 dus appearances of the Tinamou shown in 

 Plate V. 



The optic disc appears to be a broad oval, 

 made up of white and coarse nerve bundles 

 that exhibit a faintly defined, fringe-like mar- 

 gin all around its periphery. Radiating for a 

 distance of about two disc-breadths across 

 the fundus are a few, dull-gray, opaque nerve 

 fibres that finally disappear into the back- 

 ground. 



The macula is situated slightly above and 

 to the nasal side of the optic papilla. It is 

 somewhat grayer than the surrounding eye- 

 ground; above, towards the outer side and 

 below the fovea, are a few pale, bright-green 

 reflex lines. 



The pecten is a massive organ with saw-like 

 margins, the serrations being of a lighter 

 brown than the central body. The lower 

 part of the pecten is somewhat club-shaped, 

 and comes well forward toward the posterior 

 capsule of the lens. Between the projecting 

 teeth of the pectinate serrations may be seen 

 a slight stippling of pigment-like black pepper 

 grains. 



