100 



THE FUNDUS OCULI OF BIRDS 



parts of the eyeground. The fovea nasalis 

 always appears directly opposite the pupil; 

 there is no fovea temporalis visible to the 

 ophthalmoscope. 



Common Hoopoe. Upupa epops. (Figs. 

 134 and 100; macroscopic view.) This medi- 

 um-tinted fundus exhibits a single macular 

 region, — a round figure whose diameter is 

 equal to the extreme width of the papilla. 

 It is depicted by a dotted fine of pigment 

 grains that are more numerous below. The 

 fovea is shallow and not well-defined. 



The relatively large pecten has numerous 

 (about 40) convolutions; it forms a compact 

 mass that almost obscures the papilla, par- 

 ticularly when the disc is viewed from 

 above. It is covered by an ovoid cap that 

 extends from the ridge-like (upper) free 

 border about one-fourth of the distance to 

 the pectinate base, whose full length is more 

 than four times its extreme width. 



Black Hornbill. (?) Spagolobus adratus 

 An ophthalmoscopic view of the ocular 

 fundus of this species is pictured as Plate 

 XLIII, page 163 of this work. The painting 

 is of the right eye by the direct method. 

 The shimmering reflections from the trans- 

 lucent retinal elements of the fundus make 

 an accurate ophthalmoscopic view some- 

 what difficult. The principal color of the 

 eyeground is dull gray, interspersed for some 

 distance about the optic nerve-entrance 

 with a mass of fine, opaque fibres that extend 

 about a disc-length over the fundus. Beyond 

 the fibres are several dull-colored, choroidal 

 capillaries that cross the fundal field in a 

 vertical direction. Near the macular region 

 the fundus is illuminated by a brilliant 

 gray iridescence. 



The optic disc is a long, white oval, that 

 extends downward and a little inward towards 

 the inner or beak side of the head. 



The pecten is very large, the lower seg- 

 ment being carried so far forward behind 

 the iris that it is difficult to inspect it with 

 the ophthalmoscope. Instead of the usual 

 fringe of pigment the pecten presents serrated 

 margins. 



The macular region is quite circular and 

 is red-brown in color. An inner circle is 



dead white, while the foveola is represented 

 by a dark-red, central spot. There are two 

 bright rings around the macula of an irides- 

 cent, blue-green color, the fundus between 

 the two circlets being a light, luminous gray. 



European Nightjar. Caprimulgas euro- 

 peus. The fundus picture (left eye, erect image) 

 of this bird is furnished by Plate XX.IV, 

 page 163. 



The eyeground appears orange-red, every- 

 where stippled with small, red and brown 

 patches of irregular shape. Scattered about 

 are several pigmented areas, such as one 

 sees in the eyes of human subjects with 

 disseminated choroiditis. This condition, 

 somewhat modified, is seen in many owls 

 long confined in zoological gardens or aviaries, 

 and it seems to be confined to Night Birds, 

 and to be one of the results of confinement 

 and domestication. In many respects, also, 

 the eye of the Nightjar resembles that of the 

 Strigiformes except that Caprimulgus has 

 fewer choroidal vessels in the lower half of the 

 fundus. These are faintly outlined, but they 

 give to that part of the eyeground a deeper 

 red than the remainder of the background. 



The optic papilla is short and broad. 

 The antero-posterior view with the mirror 

 shows it as a dull, grayish-white body large- 

 ly covered with brown pigment dots. Its 

 margins, where it is not obscured by the mass 

 of the pecten, is much lighter in color. Radi- 

 ating from the sides of the disc, and extend- 

 ing for a short distance on either side, are 

 a few white opaque nerve fibres, which are 

 light gray and become less distinct on the 

 outer side of the papilla. 



Anna Hummingbird. Calypte anna. 

 (Figs. 101 and 135; macroscopic view.) The 

 ocular background of this species shows two 

 plainly marked macular regions, the nasal 

 fovea being, as usual, the better defined. 

 This area nasalis is seen as a black spot 

 entirely surrounded (except at the lower 

 fourth of its circumference) by a halo of 

 dark pigment grains. Outside of this is an 

 untinted zone that, in its turn, is encircled 

 by a nebulous ring broader below than 

 above. The tunics of the eyeball are cut to 

 show the temporal site of the second macular 



