Chapter VIII 



EFFECTS OF DOMESTICATION AND OTHER ABNORMAL 



INFLUENCES ON THE FUNDUS OCULI OF 



WILD SPECIES OF BIRDS 



As noted in Chapter III the eyes of only 

 healthy individuals and (as far as could be 

 ascertained) of normal wild species have been 

 chosen for the purposes of this research. In 

 practice, however, this is not as easy a task as 

 first appears, since it is on occasions difficult 

 to decide by any or all of the three principal 

 means of investigation — the ophthalmoscope 

 in living specimens, the microscope and naked 

 eye in preserved globes — whether a given 

 condition is normal or abnormal, congenital 

 or acquired. The writer's observations of 

 the eyes of both domestic and wild birds leads 

 him to believe that domestication of Birds, 

 which generally means a radical departure 

 from their natural food, exercise, manner of 

 raising their young, use of their various or- 

 gans (eyes included) and above all the effects 

 of confinement per se, is the principal cause of 

 the anomalies seen in the fundi of caged or 

 barnyard species. This difficulty in deter- 

 mining the exact character of tissue altera- 

 tions is all the greater when the suspected 

 fundus change occurs in both eyes and the 

 organs are not available for macroscopic and 

 microscopic examination. For instance, the 

 eyeground of the Spoonbill (Plate XXV) is 

 shown with a curious (and unusual) linear 

 stripe running parallel and close to the optic 

 disc. This may be an abnormal fundus con- 

 dition although the weight of evidence leans 

 the other way. 



Nocturnal birds, when caged, appear to be 

 especially affected by "Zoo" conditions. 

 The Caprimulgidae, as well as the Strigi- 

 formes, for example, are liable to acquire 

 choroidal diseases. 



While examining a number of common 

 Screech Owls, the writer found one individual, 

 about five years old and three years in captiv- 

 ity, that showed the following conditions: 

 Left eye; usual Owl fundus; well marked 

 disseminated choroiditis, affecting the nasal 

 aspect of the background more than the tem- 

 poral. The choroidal vessels show through a 

 number of atrophic areas. Usual pigment 

 spots smaller than normal, almost punctate. 

 Right fundus : the general appearance on this 

 side is of a striped gray, very much like the 

 warp and woof of some fabrics, or like the begin- 

 ning choroidal atrophy of myopia. In other 

 respects the right fundus resembles the left. 



Mr. Head informs me that in examining 

 with the mirror a Bluebird (Sialia sialis) in 

 captivity seven years, the vitreous humour 

 was found to be quite dull and foggy and the 

 fundus showed spots of an orange-red color. 

 This was very likely a diseased condition, as 

 the other eye had a cataract in it. 



The writer has examined with the ophthal- 

 moscope the eyes of a number of Turkey 

 Vultures (Cathartes aura), practically domestic 

 animals in many American towns, and found 

 few of them healthy. In one case the bird 

 had cataract in each eye. In another there 

 was beginning central opacification of the 

 lens in the left eye; the same condition more 

 advanced in the right. A third had no len- 

 ticular changes, but owing to a suspicion that 

 the fundus findings might not be those of a 

 healthy individual the findings were not in- 

 cluded in the list described in Chapter IX. 

 The following are the notes of this examina- 

 tion: Left fundus; general coloration steel 



[62] 



