666 



THE SENSES 



plexus of delicate varicose fibrils. The cornea has no blood vessels, but 

 has a rich network of lymphatic spaces. 



The Lens. The lens is a special modification of epithelium composed 

 of highly refractive material, situated just behind the iris. It is enclosed 

 in a capsule and supported in its place by the suspensory ligament, which 



FIG. 442. Vertical Section of Rabbit's Cornea, a, Epithelium of cornea, showing the 

 different shapes of the cells at various depths from the free surface; b, portion of the proper 

 substance of the cornea. (Klein.) 



is fused into the capsule around its equator. The lens is a biconvex struc- 

 ture composed of transparent fibers which are arranged in concentric 

 layers. Its posterior curvature is greater than the anterior, the radii being 

 6 and 10 mm. respectively. 



FIG. 443. 



FIG. 444. 



FIG. 443. Ciliary Processes, as Seen from Behind, i, Posterior surface of the iris, 

 with the sphincter muscle of the pupil; 2, anterior part of the choroid coat; 3, one of the 

 ciliary processes, of which about seventy are represented. X . 



FIG. 444. Laminated Structure of the Crystalline Lens. The laminae are split up 

 after hardening in alcohol, i, The denser central part or nucleus; 2, the successive exter- 

 nal layers. X 4. (Arnold.) 



The Ciliary Apparatus and the Iris. These structures are a con- 

 tinuation and modification of the choroid coat in the anterior portion of the 

 eye. Around the circumference of the cornea the choroid coat is consider- 

 ably thickened and folded in the modification known as the ciliary apparatus. 



