418 



ELEMENTARY PHYSIOLOGY 



rather less, of the thickness of these consists of a vast 

 multitude of minute, either rod-like, or conical bodies, 

 ranged side by side, perpendicularly to the plane of the 

 retina. This is the layer of rods and. cones (/> c). 

 From the front ends or bases of the rods and cones 

 very delicate fibres pass, and in each is developed a 

 granule-like or nucleus-like body (// c'), which forms a 



Pio. 135.— The Eyeball divided transversely in the Middle Line 



AND VIEWED FROM THE FRONT. 



s, sclerotic ; ck, choroid, seen in section only., 



r, the cut edges of the retina ; r.r, vessels of tlie retina springing 

 from 0, the optic nerve or blind spot; m.l, the yellow spot, the darker 

 spot in its middle being the fovea centralis. 



part of what has been termed the outer nuclear layer. 

 It is probable that these fibres next pass into and indeed 

 form the close meshwoi'k of very delicate nervous fibres, 



vitreous humour, and so is nearer the centre of the eyeball, is called the 

 inner surface ; and that surface which touches the choroid coat is called 

 the outer surface. And so with the structures between these two sur- 

 faces ; that which is called inner is nearer the vitreous humour, and that 

 which is called outer is nearer the choroid coat. Sometimes anterior, or 

 front, is used instead of inner, and posterior instead of outer. 



