402 THE ORGANS OF SPECIAL SENSE 



terminates in a dentated margin, the ora serrata, at the 

 outer edge of the ciliary processes. It then sends oft' 

 a thin, non-nervous membrane, the pars ciliaris 

 retinae, to the tips of the ciliary processes. The inner 

 surface of the retina presents at its centre an elliptical 



FIG. 141 



xx ,' Canal of Schlemm. 

 Anterior chamber. X xx ' 



& 



Cavity occupied 

 by vitreous humor. 



Sclerotic coat. 



Nerve sheath. IJA^.^PSP^ Optic 



A horizontal section of the eye-ball. (Allen.) 



spot about 2*0 mcn across, the macula lutea. In the 

 centre of this spot is a depression, the fovea centralis, 

 which, on account of the extreme thinness of the retina, 

 shows the pigmentary layer of the choroid, and hence 



