48 



THE FUNDUS OCULI OF BIRDS 



pictured by different observers, an accurate 

 photographic reproduction is much to be 

 desired. 



Probably the inventor who has come near- 

 est this ideal is Wolff (Monatsbl. f. Augen- 

 heilk., p. 447, Oct., Nov., 1907) of Berlin, 

 who has done much in the photography of the 

 human fundus. He made use of the light 

 furnished by the Zeiss projection apparatus, 

 the efferent rays being reflected into the eye, 

 through half the pupil, by a specially con- 

 trived mirror. The efferent rays passed out 

 through the other half of the pupil and were 

 focussed in a photographic camera. A circle 

 of the fundus about 10 mm. is thus illuminated 

 at one time and the resulting picture — of 

 course in gray tones — is magnified from three 

 to four diameters. The required exposure is 

 less than one-thirtieth of a second. The prints 

 showed the optic entrance, the retinal vessels 



and other gross details of the eye-ground but 

 lacked that definition without which fundus 

 reproductions are of little practical value. 



Stimulated by these experiments of Wolff 

 and by the experience of Dimmer, Thorner 

 and Neuhaus, the writer, in conjunction with 

 Dr. Earl Brown of Chicago and other experts, 

 has endeavored to solve the problem both of 

 ordinary and chromo-photography of the 

 avian fundus. It must be confessed that 

 nothing satisfactory has come of these efforts, 

 nor of the corresponding attempts, referred 

 to on p. 61, to photograph the eyeground of 

 prepared specimens. The main difficulty 

 (without entering into the details of the fail- 

 ures) in all these instances lies in the present 

 impossibility of focussing clearly at the same 

 instant all the points on such a concavity as 

 the interior of the eyeball presents, either 

 in its post mortem or its living state. 



