HISTOLOGY OF THE EYE. 95 
iii, The hyaloid membrane: the delicate elastic mem- 
brane enclosing the vitreous humour, and con- 
tinuous in front with the posterior layer of the 
capsule of the lens. 
iv. The cut edges of the retina and choroid. 
7. Remove the lens from its capsule: note its shape, more convex 
behind than in front: harden tt with spirit, or by boiling for a few 
minutes in water. 
8. Remove the vitreous humour in the hyaloid membrane - 
note -— 
i. The retina: a delicate pulpy membrane between 
the hyaloid membrane and the choroid. 
ii. The blind spot: the point of entrance of the optic 
nerve: to this spot the retina adheres firmly, 
though it can be readily removed from the 
choroid at all other parts. 
iii. The retinal vessels; radiating from the blind spot. 
C. Histology of the Eye. 
1. The frog’s eye. 
Mount in balsam oné of the prepared sections of the posterior 
part of the frog’s eye: examine with low and high powers : note :-— 
a. The sclerotic; consisting chiefly of hyaline cartilage. 
b. The choroid: a vascular plexus with much pigment. 
c. The retina: composed of the following layers from 
without inwards :— 
i. Layer of pigment cells, sending processes between 
ii, The rods and cones: a single layer of columnar 
bodies placed vertically to the surface: the rods 
are far more numerous, and much larger than 
the cones: each consists of an inner and an 
outer segment. 
iii, The outer nuclear layer: a moderately thick layer, 
well stained. 
iv. The outer molecular layer; a very thin layer, not 
stained. 
