ORGANS OF THE BOD?. 



619 



in diameter, may be observed, being the last trace of a more extensive 

 vascular covering of the anterior surface of an earlier period of existence. 

 Here we find either a single or double row of fine capillary loops, derived 

 from the anterior ciliary arteries. The calibre of the capillaries is from 

 0*0090 to 0*0045 mm. They reach as far inxvards as the fibrous portion 

 of the conjunctiva extends over the edge of the cornea. Among the lower 

 mammals they usually form a broader zone, in which case they are joined 

 by deeper, finer capillaries, springing from the vessels of the sclerotic. 

 The latter accompany the nervous twigs, supplying the part and end like- 

 wise in loops. 



Whether the cornea is possessed of lymphatics or not is a question still 

 undecided, in spite of very ex- 

 tended research. We have 

 already seen, in 133, that 

 this very peculiar tissue of the 

 cornea is traversed by a system 

 of passages containing contrac- 

 tile wandering cells, andremark- 

 able for their great dilatibility, 

 and which seem also to pos- 

 sess a species of modified lining 

 membrane. We have also 

 stated that this set of canals 

 is capable of being injected arti- 

 ficially, when, either strongly 

 distended " cornea! tubes" pre- 

 sent themselves, or finer pas- 

 sages (Bowman, Recklinghau- 

 sen, Leber, Schweigger-Seidel, 

 and Lavdowski). But the 

 fact that from them the lym- 

 phatics of the conjunctiva may 

 be eventually filled does not 

 seem a conclusive proof that 

 they are of lymphatic nature. 



The nerves of the cornea, so 

 frequently the subject of study, 

 are derived almost exclusively 

 from the ciliary branches, and 

 have two modes of termina- 

 tion. they end, namely, either 



in the epithelium or in the 



proper tissue of the cornea. 



They spread from the border 



of the latter into its substance 



in considerable number, the 



adult cornea presenting about 



60 (of a diameter of '02-0 '055 mm.), while that of the infant has only 



from 30 to 34 (Sdmisch). 



Close to the edge of the cornea these thicker or thinner twigs, as the 



case may be, are observed to contain delicate, but clearly-defined primitive 



fibrillae of from 0*0045 to 0*0023 mm. in diameter. Their perineurium 



is rich in nuclei. 



Fig. 576. Vertical section of the cornea of an infant 

 (shortened considerably, however), a, corneal tissue ; 

 6, anterior; c, posterior transparent lamina; d, lami- 

 nated, flattened epithelium of the anterior; and e, 

 single layer of the posterior surface. 



