536 BULBUS OCULI 



direction than in the vertical. That is due to the fact that 

 the sclera overlaps it to a greater extent above and below 

 than it does at the sides. The posterior, concave surface of 

 the cornea forms the anterior boundary of the anterior chamber 

 of the eyeball, and is separated by the aqueous humour from 

 the anterior surface of the iris. 



The anterior convex surface of the cornea is clothed with 

 the conjunctiva, reduced to a transparent epithelial layer. 

 On its posterior aspect there is an elastic, glassy stratum, 

 termed the posterior elastic lamina. When the cornea is 

 relaxed that membrane becomes wrinkled, and it can be 

 torn away in shreds from the proper corneal tissue. , 



Ligamentum Pectinatum Iridis. At the margin of the 

 cornea the posterior elastic lamina is fibrillar, and some of 

 its fibres are continued into the iris, forming the ligamentum 

 pectinatum iridis, whilst others are prolonged backwards into 

 the chorioid and the sclera. The ligamentum pectinatum 

 iridis bridges across the angle between the cornea and the 

 iris, and the bundles of fibres into which the posterior elastic 

 lamina breaks up in that region constitute the boundaries of 

 an annular mesh-work or sponge-like series of minute spaces 

 termed the spatia anguli iridis (O.T. spaces of Fontana). The 

 spaces communicate with the anterior chamber of the eyeball, 

 and are filled with aqueous humour. 



Tunica Vasculosa Oculi. The middle or vascular tunic, 

 frequently spoken of as the uveal tract, is exposed, in its 

 entire extent, in the eyeball from which the sclera and the 

 cornea have been removed. It is separable into three 

 parts (i) a posterior portion, the chorioidea; (2) a middle 

 part, the corpus ciliare ; and (3) an anterior segment, the 

 iris. 



Chorioidea. The chorioid is the largest part of the vas- 

 cular tunic. It lines the posterior segment of the eyeball, 

 between the sclera externally and the retina internally. It 

 is thickest posteriorly, where it is pierced by the optic nerve, 

 and becomes thinner anteriorly, as it approaches its union 

 with the ciliary body. Its superficial surface is connected 

 with the deep surface of the sclera by some lax connective 

 tissue, called the lamina fusca, and also by blood-vessels and 

 nerves which pass from the one into the other. The deep 

 surface of the chorioid is moulded upon the retina and is 

 covered with a layer of deeply-pigmented cells which usually 



