EYE OF THE ENGLISH SPARROW 419 



laries, flow to the base of the pecten where they empty into the 

 basilar vein (Bv). The direction of the flow of the blood in 

 these vessels is indicated by the arrows. This basilar vein 

 pierces the sclera a little distal to the middle of the pecten and 

 then divides into two branches. One of the branches unites 

 with the ophthalmic vein and the other with the ophthalmo- 

 temporal vein (fig. 17, P). 



The pecten consists of very loose connective tissue and pig- 

 ment cells, through which the abundant blood-vessels run. No 

 nerves can be demonstrated in the preparations at hand. I 

 cannot, therefore, agree with those who maintain that the pecten 

 is a sense organ (Franz, '08). 



The hyaloid membrane of the vitreous body is closely applied 

 to the surface of the pecten and entirely envelops it. Owing to 

 the irregularity of the folds, it is rather difficult to separate this 

 membrane from the pecten in a preserved eye. The hyaloid 

 membrane is also closely applied to the irregular ciliary proc- 

 esses and, since the distal free margin of the pecten approaches 

 close to the ciliary region (fig. 14, plate 3), one may erroneously 

 think that the pecten is attached to the ciliary bodies or possibly 

 to the lens. A careful dissection shows that it is only the hyaloid 

 membrane which bridges from one to the other. In no case 

 have I found the pecten coming in contact with the ciliary bodies 

 or with the lens. 



The pecten of the sparrow is a highly vascular organ, measur- 

 ing 2.7 mm. at the base, 1.2 mm. high, and 1.5 mm. along the 

 free margin. If the pecten were a plain body the total area of 

 the surface would be approximately 6.8 square millimeters. 

 But owing to the folded arrangement of this thin membrane the 

 total area of the surface is increased to a little over 25 sq. mm. 

 This very large surface and the rich supply of blood-vessels 

 indicate that the function of the pecten is prmiarily that of 

 nourishment. The external layers of the retina are nourished 

 by the vessels of the chorioid. The complete absence of retinal 

 vessels to nourish the inner layers of the relatively thick retina 

 necessitates some other means of nourishment for this coat of 

 the eye. The pecten contains the only blood supply from which 



