ANATOMY OF THE EYEBALL. 47 



The proper corneal membrane is composed of excessively 

 pale, flattened bundles of fibres, interlacing each other in every 

 direction. Their arrangement is lamellated, though they can- 

 not be separated into complete and distinct layers. Between 

 the bundles of fibres, lie a great number of stellate, anasto- 

 mosing, connective-tissue corpuscles. In these cells and in the 

 intervals between the fibres, there is a considerable quantity 

 of transparent liquid. The fibres constituting the substance 

 of the cornea are continuous with the fibrous structure of the 

 sclerotic, from which they cannot be separated by maceration. 

 At the margin of the cornea, the opaque fibres of the scle- 

 rotic became abruptly transparent. The corneal substance is 

 very tough, and will resist a pressure sufficient to rupture 

 the sclerotic. 



Upon the posterior, or concave surface of the cornea, is 

 the membrane of Descemet, or of Demours, elastic, transpar- 

 ent, structureless, rather loosely attached, and covered with a 

 single layer of regularly-polygonal, nucleated epithelium. At 

 the circumference of the cornea, a portion of this membrane 

 passes to the anterior surface of the iris, in the form of nu- 

 merous processes which constitute the ligamentum iridis pecti- 

 natum ; a portion passes into the substance of the ciliary mus- 

 cle, and a portion is continuous with the fibrous structure of 

 the sclerotic. 



In the adult, the cornea is almost without blood-vessels, 

 but in foetal life it presents a rich plexus extending nearly 

 to the centre. These disappear, however, before birth, 

 leaving a very few delicate, looped vessels at the extreme 

 edge. 



A great deal of anatomical interest has lately been at- 

 tached to the cornea, from researches showing the termina- 

 tion of the fine nerve-fibres in the nuclei of the posterior 

 layer of the epithelium of its convex surface, 1 and the inves- 

 tigation of the "lymph-spaces," by the use of certain re- 

 agents, the demonstration of the so-called " wandering cells," 



1 See vol. iv., Nervous System, p. 45. 

 134 



