ee 
f 
VASCULAR AND PIGMENTED TUNIC OF THE EYE. 685 
propria and possessing a thickness of 6-8 » at the centre and 10-12 at the peri- 
phery of the cornea. Less firmly attached than the anterior elastic lamina, it may 
be stripped off, when it will be found to roll up with its attached surface inwards. 
Between the ages of twenty and thirty small wart-like projections appear on its deep 
surface, near its periphery, and these increase in size and number as years advance, 
so that in old age the membrane may attain a thickness of 20 p. Towards the 
periphery of the cornea the lamina divides into three sets of fibres — anterior, 
middle, and posterior. The anterior fibres pass behind the canal of Schlemm into 
the sclera, the middle give attachment to the ciliary muscle, while the posterior are 
continued as radiating and anastomosing fibres into the substance of the iris, and 
constitute the ligamentum pectinatum iridis. A number of irregular spaces, the 
spaces of Fontana, or spatia anguli iridis, exist between the fibres of this pectinate 
ligament. Better developed in the horse and ox than in man, these spaces are 
lined by a prolongation of the corneal endothelium, and communicate internally 
with the anterior chamber and with the lymph spaces of the iris, and externally 
with the canal of Schlemin. 
5. The layer of endothelium (endothelium camer anterioris) consists of a single 
stratum of nucleated, flattened, polygonal cells, which present a fibrillar structure 
and are continued as a lining to the spaces of Fontana; this layer of endothelium 
is also reflected on to the anterior surface of the iris. 
Vascular and Nervous Supply of the Cornea.— In the fcetus the cornea is traversed, almost 
as far as its centre, by capillaries; but in the adult it is devoid of blood-vessels, except near its 
margin. The capillaries of the conjunctiva and sclera pass into this marginal area for a distance 
of about 1 mm., where they terminate in loops. All the remainder of the cornea is nourished by 
the lymph which circulates in its cell spaces and canaliculi. 
The nerves of the cornea, discovered by Schlemm, are derived from the ciliary nerves. 
Around its periphery they form a plexus, the plexus annularis, from which fibres pass into the 
cornea, where, after a distance of 1 or 2 mm., they lose their medullary sheath and ramify in the 
substantia propria, forming what is termed the fundamental or stroma plexus. Perforating fibres 
(fibre perforantes) extend from this plexus through the anterior elastic lamina and form a sub- 
epithelial plexus, from which fine filaments ramify between the epithelial cells as far as the super- 
ficial layers. From the annular and stroma plexuses fibrils pass to the substantia propria and 
come into close relation with the corneal corpuscles. 
VASCULAR AND PIGMENTED TUNIC. 
The middle, vascular, and pigmented tunic (tunica vasculosa oculi) comprises, 
from behind forwards, the chorioid, the ciliary body, and the iris (Fig. 493). 
The chorioid (chorioidea) intervenes between the sclera and the retina, reaching 
as far forwards as the ora serrata of the latter (p. 689). Dark brown or black in 
colour, it is pierced pos- 
teriorly by the optic 
Membrane of Bruch 
WZ Lamina 
3) & alee ———— chorio- 
nerve, and is here firmly =———— SESE cayillnis 
= Sas SSDS Ee. Vaca J 
attached to the sclera. 538355 ==S-0 =a = ne 
mediate 
stratum 
Thicker behind than in 
front, its outer surface is 
flocculent and 1s con- 
nected to the sclera by the 
ciliary vessels and nerves, 
and by the loose lamina 
fusca. Its inner surface is 
smooth and adheres to the 
outermost or pigmented 
layer of the retina. ~ ‘ » tht : E iB) 71 
The chorioid consists Fic. 495.— VERTICAL Peery cea OMe AND INNER PART 
of blood-vessels and fie? ofl 
branched pigment cells embedded in a loose connective tissue, and presents from 
without inwards three layers, viz.: (a) the lamina suprachorioidea ; (/) the proper 
tissue of the chorioid; and (c) a thin transparent membrane, the lamina basalis 
or membrane of Bruch (Fig. 495). 
1. The lamina suprachorioidea resembles the lamina fusca of the sclera and 
Lamina 
vasculosa 
Lamina 
— supra- 
chorioidea 
Sclera 
