ARRANGEMENT OF THE NERVE FIBRES. 207 



sions, they have diminished to fibrillae of only 0.0005 to 

 0.0003 mm. They arc said to form a new, but now very 

 narrow-meshed reticulum of the third order, the intramuscu- 

 lar plexus, between the spindle ceils of the tissue. 



From the latter proceed extremely fine filaments, 0.0002 

 mm. in size, and therefore primitive fibrillae, into the fibre 

 cells. Their discoverer, Frankenhaeuser, asserts that they 

 terminate in the nucleoli, but Arnold is already doubtful on 

 this point. 



A few years ago, as I examined the muscular vascular walls 

 of the frog, by the aid of the best customary methods, I saw 

 only nerve plexuses. Klein also went no further. I suspect 

 that the predecessors — in this most difficult department — have 

 also deceived themselves. 



The nerves of the cornea of the eye have been the object 

 of very extensive researches for years. We here meet with a 

 twofold manner of termination ; one in the proper corneal 

 tissue, and another in the epithelial stratum of the free an- 

 terior surface The latter is certainly sensory, the former 

 most probably of a motory nature. 



The corneal nerves enter at the periphery as a bundle of 

 fine, at first medullated fibres. The medullary sheath is soon 

 lost ; we have pale filaments to which must here, as in the 

 smooth muscles, be at first ascribed the signification of the 

 axis cylinder, and subsequently of the primitive fibrillae (p. 

 196). In the cornea we also meet, from behind forwards, 

 with a series of nerve plexuses, lying one over the other, with 

 evident divisions of the fibres. 



A considerable contingent of the latter terminate in the cor- 

 neal tissue. How, is unknown. A former statement of 

 Kuehne's, according to which the primitive fibrillae were said 

 to finally unite with the corneal cells (p. 56), could not be 

 confirmed. 



Cohnheim, after the example of Hoyer.has shown that from 

 the most superficial nerve plexus of the cornea the finest nerve 

 filaments (primitive fibrillae or fasciculi of the latter) pass into 

 the stratified, flattened epithelium of the above mentioned 



