544 



NERVES OF THE CORNEA. 



[sect. 224. 



interior a clear juice, in which clear round cells, exactly like 

 lymph-corpuscles^ were to be seen; these were usually in small 

 numbers, but occasionally were very numerous. 



The nerves of the cornea, which were discovered by Schlemm, 



are derived from the nervuli ciliares, enter this coat at the anterior 



circumference of the sclerotic (in the rabbit, according to Rahm, 



at the posterior half of the globe), and then pass from it into the 



Fig. 218, fibrous layer of the cornea. 



Here they are readily found at 

 the border, forming, in man, 

 twenty-four to thirty-six trunk- 

 lets of various degrees of fine- 

 ness, but scarcely ever exceed- 

 ing 0*02'" in diameter. These 

 nerves are distinguished by 

 their mode of distribution, 

 which is effected by numerous 

 j||K- j \ \l \ dichotomous divisions and 



anastomoses, so that a wide 

 nervous network is produced, 

 extending through the whole 

 cornea ; they are, however, 

 especially remarkable for the 

 circumstance, that they contain fine, dark-bordered, primitive tubes 

 (o*ooi'" to 0*002"'), only at the margin of the cornea, within a 

 zone half a line to one line in average breadth; while in their 

 further course they possess only non-medullated fibres, completely 

 clear and transparent, measuring 0'0003'" to o'Ooi'" at the most: 

 thus, in any case, they do not impede the passage of the rays of 

 light more than the other elements of the cornea, as is evident 

 from the difficulty with which they are traced under the micro- 

 scope. Bifurcations of the primitive tubules present themselves, 

 though rarely, in the trunks of these nerves, but never in the 

 plexus formed by them, the condition of which, however, can 

 scarcely be fully investigated, on account of its paleness. This 

 plexus lies in the proper cornea, but nearer to the anterior surface ; 

 and, since no trace of free terminations of nerve-fibres is to be 

 seen, it would appear to consist solely of anastomosing twigs of the 

 finest kind, so that, if not in the form of loops, still some con- 

 nection of the nerve-tubes with one another may be assumed. 



The blood-vessels of the conjunctiva comece, of healthy individuals, are very 

 scanty, and those which are figured hy Romer (Ammon's Zeitschr. v., 21, tab. i. 



Nerves of the cornea of the rabbit in their 

 coarser ramifications. The distance to which the 

 dark-bordered tubes extend in the trunks is 

 here expressed by the darker portions of the lines. 



