FUNDUS OCULI OF BIRDS IN PREPARED SPECIMENS 



61 



area — single or double, sometimes associated 

 with a band area, sometimes not — with clearly 

 outlined margins and a deep fovea and dis- 

 tinct foveola. In others the fovea is shallow 

 and the macular borders are with difficulty 

 differentiated from the fundal retina. 



Photography of the Fundus Oculi in 

 Prepared Eyeballs 



Attempts similar to those of Wolff and 

 others, mentioned in Chapter VI, to photo- 

 graph the interior of the posterior half of the 

 eye have been made with some success in the 

 case of prepared eyes. The difficulties that 

 surround these attempts, although fewer than 

 with the living subject, are as yet unsur- 

 mounted so far as minute and exact fundal 

 details — the chief object to be attained — 

 are concerned. Photography furnishing a 

 clear and sharp definition of small objects 

 arrayed at various points in one concave sur- 

 face is as yet impossible — hence the blurred 

 appearance of pictures of the vertebrate eye- 

 ground so far published. Even the best of 

 these — the enlarged stereoscopic photo- 

 graphs that illustrate Arthur Thomson's 

 Anatomy of the Human Eye (London, 1912), 

 the carefully prepared original photographs 

 in the beautiful atlas of Fritsch, and the 

 stereographs of George Dixon — hold out 

 little hope that similar processes may be of 

 use in depicting avian eyegrounds. Only 

 the laborious pen and brush of the careful 

 and competent artist-ophthalmoscopist can 

 so far be depended upon to depict the mac- 



roscopic appearances of these complicated 

 tissue arrangements. 



R. H. Elliot (The Lancet, p. 830, Nov. 11, 

 1916) has developed a method of photograph- 

 ing prepared eye specimens of which the 

 writer has had no personal experience, but 

 which he believes may be of value to the 

 investigator. Elliot regards the following 

 points of importance: The photograph must 

 be taken in water, without the intervention of 

 glass or other similar material. The source 

 of light must be good and even. The camera 

 must be placed vertically above the object 

 so as to avoid reflections. The object of the 

 photograph must be placed so that its image 

 will occupy the center of the plate, and a 

 method of adjustment should be available to 

 secure this end with a minimum of incon- 

 venience. A simple arrangement is neces- 

 sary to fix the eye in position during the 

 whole period of exposure. To save unneces- 

 sary retouching the object should be photo- 

 graphed lying on a dark and uniform surface 

 to obviate the background disturbing the 

 attention of those viewing the picture. Care 

 should be exercised in the choice of a camera 

 and exposure periods must be carefully 

 studied. For the making of lantern-slides 

 the contact method was recommended, and 

 attention was directed to the following points : 

 correct exposure; the preparation of plates 

 for exposure; development and fixation of 

 the slides; the drying of the plates; and the 

 reduction, intensification and varnishing of 

 slides. 



