217 
On the Srructure of the Retina. By Tuomas NunnzE ey, 
F.R.C.S.E., Lecturer on Surgery in Leeds School of 
Medicine, Surgeon to the Leeds General Eye and Har 
Infirmary, &e. 
Tue retina is the sentient part of the eye, for which all 
the other textures are formed, and to which they may be said 
to be subservient. It is coextensive with the choroid proper ; 
it covers the whole of the convex portion of the vitreous 
humour, and is covered by the choroid. It terminates in a 
serrated line, ora serrata, which is readily seen with an inch 
lens, just where the ciliary processes are continuous with the 
choroid. There is, according to some anatomists, a circular 
blood-vessel running near to this edge, if so, it is probably 
a vein, but it rather appears as a series of capillary loops of 
the central artery. Some of the older anatomists and opti- 
cians described the retina as being continuous over the 
anterior surface of the crystalline lens, an opinion which has 
been adopted to a great extent by Arnold, who describes and 
figures the retina as being continuous with the ciliary body 
and processes to the edge of the lens,*—wpars ciliaris retine 
and processus ciliaris retine. This, however, is, without 
doubt, an error ; though the retina does not terminate wholly 
and absolutely at the ora serrata, as is commonly described. 
The nervous structure here ends, but there is, contimuous 
with the suspensory ligament of the lens, a cellular layer, as 
far as the edge of the lens: this is best seen after the eye 
has been kept for some time in spirit or Goadby’s solution, 
by which the layer is rendered opaque and white. Its con- 
tinuity with the retina may then be readily traced, and, 
indeed, in some eyes it looks so hke a continuation of the 
whole retina as to render the microscope essential to prove 
that the nerve-structure is not so prolonged.t The retina 
has, until very recently, been described as the terminal ex- 
pansion of the fibres of the optic nerve into a membrane. 
It is, however, much more than this; it is one of the 
most complex, perhaps the most complex, structure to be 
* ¢ Tcones organ. sen.,’ tab. 3, fig. 2. 
{ In one instance of an alligator, I find a memorandum I made at the 
time of the dissection, to the effect that the retina was traceable to the 
edge of the lens; but as this was made before I was so well acquainted 
with the different structures in the retina, and the eye was not very fresh, 
I should not rely upon this apparent exception, but look carefully at these 
parts when opportunity again offers a similar creature. 
