Chapter III 



COLLECTION, SELECTION AND PREPARATION OF MATERIAL 



BIBLIOGRAPHY 



Although the eyes of many hundreds of 

 species have been examined by the writer 

 ophthalmoscopically and otherwise his pur- 

 pose in this work is to describe as nearly as 

 may be the conditions found in the fundi of 

 such birds (especially of living birds) as are 

 most likely to be useful in a study of com- 

 parative ophthalmology. To this end he 

 has confined his attention to normal wild 

 species and has studiously avoided domesti- 

 cated, domestic or otherwise abnormal birds. 

 It is in these more or less tame species that 

 numerous variations from the normal eye- 

 ground are seen; consequently it is quite im- 

 possible to deduce from fundus examinations 

 of tame or diseased birds any physiological 

 conclusions worthy the name. This choice 

 of normal, wild birds has added somewhat 

 to the difficulties of the task. Domesticated 

 animals are the most accessible and the 

 easiest to examine; but any one who has 

 made a study of the matter will soon discover 

 that, as in Man, specific variations of the 

 fundus picture in domesticated species are so 

 numerous as to render it impracticable for 

 any one, even in a long lifetime, to make a 

 complete investigation of the ocular back- 

 ground in more than a few of these animals. 

 Even in an examination of the eyes of birds 

 in a public aviary the length of time the 

 individual has been held in captivity is of 

 importance from the ophthalmoscopic stand- 

 point; recently caught, healthy specimens are 

 always preferable to birds that have been 

 long confined and exposed to the unwonted 

 surroundings of cage life. 



In addition to such wild birds as are acces- 

 sible in private collections or that are to be 



found in every zoological garden or park, 

 the field naturalist may himself, or by proxy, 

 trap or shoot the specimens he needs. Many 

 birds can be procured through collectors em- 

 ployed by Museums and Colleges, either as 

 duplicates or in conjunction with the col- 

 lectors' other work. The writer, armed with 

 a proper license, has made several collecting 

 trips of this kind and has in this way been 

 able to examine the fundi of many disabled 

 or recently killed birds. 



A self-luminous ophthalmoscope (see page 

 30) and a large opaque, black umbrella are 

 the most useful implements for field work. 

 A few minutes before and after the death 

 of the specimen one finds the pupil widely 

 dilated, so that the ocular interior can be 

 readily explored. Birds that are uninjured 

 or merely "winged" are placed in a box or 

 cage and carried to the laboratory or dark 

 room, there to be examined ophthalmo- 

 scopically at greater leisure. See Chapter VI. 



(For macroscopic studies of the fundus in 

 prepared material the bird's head should be 

 placed in a preserving fluid — preferably 

 Perenyi's — a few minutes after death. In 

 collecting specimens the following rules should 

 be observed: 



1. When possible, secure at least three 

 heads of each species. 2. Immediately after 

 death incise the skin about the neck well 

 below the head and carefully remove the skin 

 from the head by pulling it forward, wrong 

 side out, over the head, cutting the thin mem- 

 branes about the eyes (at the margin of the 

 orbit) without injury to the eyeballs. If the 

 eyes or their appendages are cut or injured 

 in any way the specimen is rendered useless. 



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