420 JAMES ROLLIN SLONAKER 



such nourishment could be readily o.btained. This is accom- 

 plished by osmosis through the vitreous humor. 



In my opinion, then, the function of the pecten is principally, 

 if not wholly, that of nourishing the inner structures, of the 

 eye. I cannot, therefore, agree with Beauregard ('79) or with 

 Wood ('14) who claim that the pecten may serve as a screen to 

 prevent the rays of the sun from injuring the retina. Since the 

 pecten lies posterior and ventral to the point of acute vision and 

 in a plane almost parallel with the rays of light entering the 

 eye, it would be almost impossible for it to serve as a screen. 



Neither can I agree with Abelsdorff ('98) and Franz ('08) who 

 maintain that the pecten is a sense organ for determining the 

 intraocular pressure during accommodation. I have found no 

 anatomical structures which would indicate that the pecten is 

 either a sense organ or plays any part in accommodation. My 

 observations confirm those of Blochmann ('11), who states that 

 the pecten consists exclusively of connective tissue and blood- 

 vessels. 



THE RETINA 



The retina of the sparrow eye covers the whole of the fundus 

 with the exception of the region of the entrance of the optic 

 nerve. It terminates at the ora serrata near the posterior ends 

 of the scleral plates (fig. 30; plate 7, fig. 33, and plate 8, fig. 43). 

 If the front of the eye were cut off at the ora serrata the plane of 

 section would cross the optic axis about two-thirds its length 

 from the fovea and would pass through the lens slightly behind 

 its center. The total area of the adult sparrow retina is approx- 

 imately 85 sq. mm. 



As in other vertebrates, a modified portion of the retina, the 

 pars ciliaris retinae, extends forward over the ciliary processes 

 forming the uveal pigment, and over the posterior surface of 

 the iris as the pars iridica retinae. This portion contains no 

 nerve-fibers. 



WTien the front of a preserved eye is removed by an equatorial 

 section, the retina appears as a uniform gray surface except at 

 the optic nerve entrance and at the area centralis and fovea 

 (plate 1, fig. 1). The optic nerve entrance is ahnost completely 



