102 



THE FUNDUS OCULI OF BIRDS 



area is probably the macular region; at least 

 it corresponds to its usual locality in other 

 orders and presents the characters one might 

 expect, knowing the habits of the animal. 



Red-shafted Flicker. Colaptes mexican- 

 us. (Figs. 104 and 137; macroscopic view). 

 The ocular fundus of this species presents a 

 single fovea (or what in Man is called the 

 oveola) that seems larger than usual; at any 

 rate the central black spot is more pronounced 

 than in most Birds. It has no well-defined 

 macular ring but appears to have a place in 

 the uniformly dotted retina about half a disc 

 length above and slightly to the nasal side of 

 the anterior optic terminal. 



The pecten has seventeen double coils (34 

 single convolutions) on either side of a promi- 

 nent and rather deep keel or ridge that unites 

 them above. Of these coils two stand at 

 right angles to the keel, two are slightly curled 

 on themselves and present a concavity 

 towards the posterior free border, while the 

 remainder look in the opposite direction with 

 varying degrees of concavity. 



Red-headed Woodpecker. Melanerpes 

 erythrocephalus. (Figs. 103 and 138; macro- 

 csopic view). The general appearance of 

 this fundus much resembles that of the Red- 

 shafted Flicker. It is true that here the 

 macular field is defined by a boundary of faint 

 printed dots, but these are hardly distin- 

 guishable, except at the infero-nasal quad- 

 rant, from the pigment of the neighboring 

 retina. In the center of the sensitive area 

 is a single black spot surrounded by a cloud 

 of dark granules that are wanting below, in- 

 tended to depict the fovea. 



The pecten has 34 single convolutions. Its 

 structure also closely resembles that of the 

 Flicker just described, but the former is 

 larger, the folds are heavier, and the uniting 

 keel is wider and deeper. 



Gila Woodpecker. Centurus uropygialis. 

 An ophthalmoscopic view of the fundus oculi 

 of this bird, as shown in Plate XL VII, page 

 167, shows it to be dull -gray tinted with 

 yellow, and nearly uniformly charged with 

 minute, gray dots. 



At the superior termination of the optic 

 disc (on the nasal side) is a small gray depres- 



sion, partly surrounding a central, well- 

 marked and glistening white dot. Within 

 this area are, also, several golden yellow dots, 

 which can be seen only when the reflected 

 light of the ophthalmoscopic mirror falls 

 obliquely upon them. Owing to the limited 

 number of this species that Head and the 

 writer were able to examine it was impossible 

 to say whether the punctate deposits last 

 mentioned are normal or pathological. Fur- 

 ther investigation of additional specimens, 

 both ophthalmoscopically and microscopically, 

 will be necessary to decide the question. 



The outlines of the optic nerve entrance 

 are well defined, and the central area of the 

 papilla at its union with the pecten is dull 

 orange stippled with dark brown pigment, 

 like pepper grains. The papilla is fringed 

 with coarse white fibres. A large number 

 of translucent nerve fibres radiate from the 

 edge of the optic disc on all sides; they be- 

 come fainter and fainter as they approach 

 the fundal periphery and finally disappear. 



The pecten, of the usual chocolate brown 

 color, reveals several corkscrew convolutions. 

 It comes well forward towards the lens, and 

 presents a massive, club-shaped appearance. 

 In most respects this fundus picture re- 

 sembles the eyeground of the Greater Spotted 

 Woodpecker. 



Great Spotted Woodpecker. Dryobates 

 vel Dendrocopus major. The fundus picture 

 of this species is seen as Plate XL VIII, page 

 167. The color of the eyeground is a uni- 

 formly dull but definite gray, interspersed 

 with a large number of small, gray dots. Be- 

 low the optic disc and pecten are a few faint, 

 orange-red choroidal vessels. 



The optic disc is apparently built of a mass 

 of brilliant, white, opaque fibres, very short 

 and thick. In the form of radiations from 

 the margins of the papilla towards the fundal 

 periphery run many gray, opaque nerve 

 fibres, that appear to occupy a plane lower 

 than the white elements of the disc. 



The pecten has three corkscrew convolutions 

 on the disc, while its lower part forms a club- 

 shaped mass of a deep chocolate-brown color 

 that appears to come well forward towards 

 the lens. 



