THE EYE. 359 



or in the Dog, Ox, Sheep, Pig, and Rabbit. But it is now well 

 known that the commencements of lymphatics, for once when 

 they are distinct (in the intestinal villi for instance), escape the 

 sight perhaps twenty or thirty times. Nevertheless, in this 

 case there seems to be every reason for caution. Should the 

 vessels in question not be lymphatics, they might be regarded 

 as pathological excavations, or as transformations of earlier 

 embryonic corneal vessels; but the manifest limitary membrane 

 of the canals is opposed to the former supposition, and the 

 latter is upset by the circumstance that they occurred in the 

 same plane with true vessels, and did not enter into the least 

 anastomosis with them. 



The nerves of the cornea discovered by Schlemm, are derived 

 from the nervuli ciliares, penetrate the sclerotic at its anterior 

 border (in the Rabbit, according to Rahm, in the posterior half 

 of the globe), and thence enter the fibrous layer of the cornea. 

 In Man, they are readily found at the margin of that tunic, in 

 the form of 24 — 36 finer and thicker twigs, but scarcely ex- 

 ceeding 0-02'" in size. What Fi 2 98. 

 especially characterises these 

 nerves, is not so much their 

 mode of distribution, which 

 takes place with numerous 

 bifurcations and anastomoses, 

 so as to produce a wide nervous 

 plexus extending throughout 

 the cornea, as the circum- 

 stance that they still contain 

 dark-bordered, though fine 

 (O'OOl — 0-002"') primitive 

 tubules, only at the margin of 

 the cornea, in a zone not always of uniform width, \ — 1'" broad, 

 and in their further course present nothing but non-medullated, 

 perfectly clear and transparent fibres, 0*0005 — 0-001'" at most 

 in diameter, so that they offer, at any rate, no more obstacle 

 to the passage of the rays of light than the other corneal ele- 

 ments, as is evident from the difficulty with which they are 

 traced under the microscope. The trunks of these nerves ex- 

 Fig. 298. Coarser ramifications of the nerves of the cornea of the Rabbit. Where 

 the trunks are represented as dark, they contain dark-bordered primitive fibres. 



