466 



THE EYE. 



the nerve itself, into the superior and inferior papillary artery and 

 vein. Both the latter again divide into two branches, the nasal 

 and temporal arteriole and venule, known, according to their posi- 

 tions, as the superior and inferior nasal and temporal artery and 

 vein. 



Besides these vessels, two small arteries also arise from the 

 trunk of the central artery itself, and extend to the macula. Two 

 similar vessels extend toward the nasal side as the superior and 

 inferior median branches. Within the retina itself the larger ves- 

 sels spread out in the nerve-fiber layer, forming there a coarsely 

 meshed capillary network connected by numerous branches with a 

 finer and more closely meshed network lying within the inner 



'- - - Vascular 

 plexus of 

 macula lutea 

 with wide 

 meshes. 

 Fovea centra- 

 1 is, free from 

 vessels. 



Fig. 363. Injected blood-vessels of human macula lutea ; surface preparation ; X 



nuclear layer. The venous capillaries of this network return as 

 small venous branches to the nerve-fiber layer, in which they form 

 a venous plexus, side by side with the arterial plexus. 



The arteries of the retina are of smaller caliber than the veins. 

 The larger arteries possess a muscular layer ; the smaller, only an 

 adventitia. All the vessels possess highly developed perivascular 

 sheaths. The visual-cell layer is nonvascular, as are also the fovea 

 centralis and the rudimentary retinal layers lying anterior to the 

 ora serrata. 



The arteries of the retina anastomose with one another solely by 

 means of capillaries (end-arteries), and it is only in the ora serrata 

 that coarser venous anastomoses exist. 



