*SrSi.Sri%f ] Eisiology of the Eye. 239 
uvea or uveal surface. The cells are less regular in size and shape 
than those of the corresponding epithelium of the choroid. 
Fig. 8. Nervous Ciicle. 
Ciliary 
Processes. 
Pupil. 
Nerves of Iris, prepared with Osmic Acid. 
The front of the iris also has an epithelium. It is much more 
delicate than that on the hack, and more difficult to demonstrate. 
Weak solutions of nitrate of silver are useful for this purpose. 
In the Choroid we recognize two subdivisions — a larger poste- 
rior portion, reaching from the optic nerve forwards as far as the 
jagged line which marks the termination of the nervous retina, ora 
serrata ; and a smaller anterior portion, lying between this and the 
iris, which we call the ciliary body. So much of this latter as 
belongs properly to the apparatus of accommodation, it is not my 
purpose to describe in this lecture. My present remarks will relate 
more particularly to the posterior segment. Its principal character- 
istics are, its pigmentation and its great vascularity. This latter 
much exceeds that of the iris ; and, further, there is a peculiarity 
in the arrangement of the blood-vessels — the capillaries lie apart 
from the large vessels. 
Enumerating the different tissues in the order in which they 
occur in passing from the inner to the outer surface of this coat, we 
first meet with a pavement-epithelium, borne upon a structureless 
