THE EYE. 



Structure of the sclerotic. The sclerotic coat is formed of bundles of 

 connective-tissue fibres, and yields gelatine on boiling. Its white fibres are com- 

 bined with fine elastic elements, and amongst them lie numerous connective- 

 tissue corpuscles lodged in cell-spaces, but not by any means so regularly arranged 

 as in the cornea. Some of the cells are pigrnented. The bundles are disposed in 

 layers both longitudinally and transversely, the longitudinal arrangement being 

 most marked behind and at the surfaces, the transverse or circular near the corneal 

 margin. The layers communicate at intervals so as not to be separable for any 

 distance. 



Both externally and internally the sclerotic is covered with flattened endothelial 

 cells, which are reflected over the muscles, vessels, nerves, and connecting bands of 

 tissue which pass from it to the capsule of Tenon and the choroid coat respectively. 

 The lamina fusca resembles in structure the lamina suprachoroidea of the choroid 

 coat (p. 25). 



The anterior zone of the sclerotic from about the line of attachment of the 

 tendons of the recti muscles forwards to the cornea, is covered by the conjunctiva 



Fig. 17. TERMINATION IN END-BULBS OP THE 



NERVES OF THE CONJUNCTIVA. (LongWOrth.) 



which is reflected on to the globe from the 

 eyelids, and which is connected with the 

 sclerotic by loose areolar (subconjunctival) 

 tissue. This part of the conjunctiva is 

 formed of somewhat dense connective 

 tissue covered by a stratified epithelium 

 of some thickness. It is a fairly vascular 

 membrane, and contains a network of 

 lymphatics, which begin at the edge of the 

 cornea by tapering capillaries. Its nerves 

 are mostly medullated : some pass towards 

 the cornea, others end in the membrane 

 itself, many in end-bulbs (W. Krause). 



A few blood-vessels derived from the 

 short ciliary and the anterior ciliary 

 arteries, permeate the fibrous texture in 

 the form of a network of capillaries with 

 very wide meshes. Those from the anterior ciliary emerge from under the tendons 

 of the recti muscles, dividing into branches as they pass towards the margin of the 

 cornea. Before reaching this, however, they dip into the substance of the sclerotic, 

 and they here take on a radial disposition in the thickness of that coat. Other 

 vessels derived from the posterior ciliary arteries form a wide-meshed network at 

 the surface of the sclerotic in its posterior three-fourths, and like those from the 

 anterior ciliary communicate freely with deeper vessels in the substance of the 

 membrane. At the posterior part of the sclerotic its vessels are continuous with 

 those of the dural sheath of the optic nerve. Around this nerve the scleral 

 branches of the posterior ciliary arteries form an arterial circle (circulus Zinnii), 

 which gives branches to the optic nerve and choroid as well as to the sclerotic. The 

 vessels of the conjunctival membrane, which are derived from the palpebral and 

 lachrymal arteries, are readily distinguishable from those of the subjacent sclerotic 

 by their more tortuous course, and by the fact that they shift upon the globe when 

 the conjunctiva is pulled upon. Near the edge of the cornea they communicate with 



