Chapter IX 



THE OPHTHALMOSCOPIC AND MACROSCOPIC APPEARANCES 

 OF THE FUNDUS OCULI IN VARIOUS ORDERS OF BIRDS 



That one may properly answer many questions 

 involved in the anatomy and physiology of the 

 important organs and tissues that constitute 

 the eyeground in Vertebrates it is necessary to 

 consider not only the ophthalmoscopic, but the 

 macroscopic and, in some instances, the mi- 

 croscopic findings. Although none of these 

 methods of research has as yet been carried out 

 with any approach to completeness yet the his- 

 tology of the retina and other visual organs has 

 been satisfactorily studied in Man, and a few 

 other species of Vertebratse, by Cajal, Greeff 

 and others. Little attention has, however, 

 been paid to the other two forms of investiga- 

 tion, that is to avian ophthalmoscopy or to what 

 may be termed avian ophthalmomacroscopy. 



Ophthalmoscopy is, in effect, a demonstra- 

 tion of the actual (comparative) size and rela- 

 tive position of the principal parts — nerves, 

 bloodvessels, [oil droplet (?)] dots, organs of 

 special sense — as well as the actual coloration 

 of the fundus oculi of the living Bird. Macro- 

 scopy, on the other hand, reveals some details 

 of the Bird's eyeground not apparent or only 

 faintly apparent to the ophthalmoscope. For 

 example, the extent and other exact relations 

 of some of the areas of acute vision, as well 

 as definite, lateral views of the pecten, are 

 better determined by naked-eye examinations 

 of prepared specimens than by viewing them 

 through the pupil of animate species.* To 



*The dots that besprinkle the fundus in the black 

 and white drawings (to indicate the macroscopical 

 appearances of the fundus in preserved specimens) are 

 merely the artist's device to depict the concavity of 

 the eyeball, elevation of parts, etc., and have nothing 

 to do with the f undal dots and other coloration so well 

 shown in the colored plates. 



this may be added, as elsewhere pointed out, 

 that in certain instances the fine anatomy and 

 exact relations of certain organs and tissues of 

 the background of the Bird's eye can be deter- 

 mined only by a microscopical examination of 

 stained and injected sections of the parts. 



The following species (healthy adults) have 

 been examined either with the ophthal- 

 moscope or by inspection of prepared eye- 

 balls, or by both methods. In a number, 

 also, the eyes have been sectioned and ex- 

 amined microscopically. These findings have 

 been mostly pictured in the text or by ap- 

 pended colored plates, and will now be 

 described. 



A. RATITAE 



Struthioniformes 



Nubian or Northern Ostrich. Struthio 

 camelus. (Figs. 116 and 77; macroscopic 

 view). The black and white drawing of this 

 fundus shows a large, regularly oval papilla 

 sprinkled with pigmented dots and circled by 

 a well-defined border. 



The foreshortened view of the pecten gives 

 one the impression of an octopus-like figure 

 lying upon and almost covering the surface of 

 the optic disc, which is plainly visible beneath 

 and sprinkled with pigment dots. There are 

 readily counted twenty-four pectinate con- 

 volutions (12 double folds) that meet above 

 and are joined to an irregularly ovoid body — 

 the crest or free margin of the marsupium — 

 apparently by a sort of purse-string action. 

 The folds of the pecten are extremely thin and 

 entirely unlike the great majority of the con- 

 volutions in carinate birds. 



[64J 



