OPHTHALMOSCOPY OF THE FUNDUS IN LIVING BIRDS 



35 



large, black umbrella, or make the examina- 

 tion in a darkened tent; in public or private 

 aviaries the examination can often be made 

 after sundown. 



A four dioptre convex lens must be placed 

 in front of the eyehole of the mirror. This 



species that present invariable ophthalmo- 

 scopic pictures. It will be found that after 

 two or three generations of inbreeding, con- 

 finement and domestication, changes occur 

 in the ocular apparatus coincident with varia- 

 tions in other parts of the organism. 



Fig. 23 



Method of Examining the Bird's Eye with the Self-luminous 

 Electric Ophthalmoscope. 



"indirect" method (see, also, page 29) gives a 

 comparatively small, inverted image of the 

 ocular fundus. It corresponds to the low 

 power lens which one uses in the preliminary 

 examination of a microscopical section. 



The examination by the erect image will, on 

 the whole, be found the most satisfactory 

 method, although, as in viewing the human 

 fundus, it is advisable to use the indirect plan 

 at the outset. The self-luminous ophthal- 

 moscope is quite satisfactory for both these 

 purposes. 



In making an examination of the avian 

 fundus it must be remembered that it is wild 



The facility (or otherwise) with which the 

 ophthalmoscope can be used depends, in a 

 large measure, upon the conduct of the bird 

 under examination. For instance, it is im- 

 portant that the macular region be carefully 

 explored and it can generally be seen, but 

 throwing the light on this very sensitive area 

 often makes the animal restless and the 

 greatest gentleness should be observed to 

 keep it quiet if a complete examination is to 

 be made. Most specimens, not excepting 

 the Eagles, Hawks, Vultures and other large 

 birds can be hypnotized and so quieted for the 

 period of an ophthalmoscopic examination. 



