66 THE EYE. 
Describe the layers of the cornea. . 
First, the anterior corneal epithelium consists of a layer of stratified 
epithelium ; next is a dense transparent membrane made up of closely- 
packed fibrillee and called the anterior basal membrane, or lamina 
elastica anterior. The middle layer or substantia propria cornezx is 
composed of connective-tissue fibres made up of clear fibres. Lying 
upon this layer is a thin structureless membrane called the membrana 
elastica propria, or membrane of Descemet, which in its turn is cov- 
ered by a simple layer of epithelium. 
Describe the choroid coat. 
It is composed of four indistinct layers. Its outer layer lies next 
to the lamina fusca of the sclerotic, forming the inner wall of the 
lymph sac, between the sclera and choroid, and is called the lamina 
supra-choroidea. This layer is made up of a series of connective- 
tissue membranes, containing delicate elastic fibres and irregular and 
branching pigmented cells. The next layer is composed of blood- 
vessels of the choroid and is called the external vascular layer, or the 
layer of Haller. Within this is a dense network of capillary blood- 
vessels forming the third coat and called the chorio-capillaris. Lastly, 
the inner layer of the choroid is composed of an extremely delicate, 
finely-striated membrane, the lamina vitrea, or membrane of Bruch. 
Describe the iris. 
It is a thin connective-tissue membrane perforated at its centre by 
an opening (the pupil), and consisting chiefly of interlacing connective- 
tissue fibres, and numbers of irregular and branching pigment cells, It 
contains numerous bloodvessels with thick walls, and near the pupil- 
lary opening are seen smooth muscle fibres circularly arranged 
(sphincter pupille). Radiating toward the periphery from this ring 
are other smooth muscle fibres (dilator pupille). The anterior sur- 
face is covered by a single layer of epithelial cells. The posterior 
surface is composed of a layer of densely pigmented, irregular, poly- 
hedral cells forming the uvea. 
Name the layers of the retina. 
1—Membrana limitans interna. 
2—Layer of nerve fibres. 
3—Layer of nerve or ganglion cells. 
4—TInternal molecular layer. 
5—Internal nuclear layer. 
6—External molecular layer. 
