VESSELS AT THE MARGIN OF THE CORNEA. 331 



c. THE MARGIN OF THE CORNEA. 



At the anterior part of the sclerotic, where it is invested by 

 the conjunctiva, as far as to the corneal margin, two vascular 

 layers may be distinguished ; a deep episcleral or sub-con- 

 junctival layer, formed by the branches of the anterior ciliary 

 vessels, and a superficial or conjunctival vascular layer, which 

 only communicates with the former at the margin of the 

 cornea. 



The anterior ciliary arteries, after their emergence from the 

 muscles, run very tortuously towards the margin of the cornea, 

 near which they give off a number of fine episcleral branches, 

 whilst their principal branches perforate the sclerotic. As a 

 rule, two vessels proceed from each muscle, with the exception 

 of the rectus externus, from which only one is given off. In 

 many cases an artery to the temporal side proceeds from the 

 palpebral vessels, and running in the connective tissue, per- 

 forates the sclerotic near the margin of the cornea. 



The anterior- ciliary veins are distinguished from the arte- 

 ries by their smaller size (consequent on their much more 

 insignificant perforating branches) and the straighter course of 

 their coarser branches. Their episcleral branches, on the other 

 hand, are larger than those of the arteries, as is usually the case 

 where the two sets of vessels supply the same region. They 

 communicate by a very rich plexus of fine veins with rather 

 small polygonal meshes, which, on account of its position, has 

 been named the episcleral venous plexus, and surrounds the 

 cornea, forming a zone of about four millimeters in breadth. 



The episcleral branches of the arteries and veins nearly cor- 

 respond in their ramifications, the arteries being constantly 

 finer, and running straighter than the veins in opposition to 

 the relations of the trunks. 



After giving off small branches to the sclerotic, they run with 

 frequent subdivision and numerous arched communications 



in the second part of which (Max Schultze's Archiv, Band vi., pp. 261 

 362) the author maintains that the canal of Schlemm is a lymphatic 

 cavity, and has no connection with the ciliary plexus, appeared after 

 the above account was written. I must decidedly support my own view 

 in opposition to that of M. Schwalbe. 



