CiAcciOj on the Nerves of the Cornea, 
85 
the mouse. In the nerves distributed to the cornea of the 
sparrow scarcely any change in the relative position of the 
primitive nerve-fibres is observed. The change alluded to is 
effected in this manner : — A fibre running close by the side 
of another is seen to leave it and unite with a new one^ with 
which, after proceeding for some distance, separates again 
and passes with another fibre or with its first companion. 
Some observers have asserted that primitive nerve-fibres 
are seen dividing, although seldom, in the trunks of the 
nerves of the cornea, but such division never occurs in the 
network or plexus formed by them. This assertion is not 
supported by actual observation. When we consider the 
number of the primitive fibres contained in the trunks, and 
compare it with the numerous fibres into which they re- 
solve themselves, we must come to the conclusion either 
that the fibres of which the nerve- trunks are composed divide 
and subdivide freely, as the trunks themselves divide and sub- 
divide ; or that what appears in the trunks to be a primitive 
fibre is not a single fibre, but a compound one. I have tried 
many times to follow some of these primitive fibres as far as 
I could, and I have always seen them gradually reduced into 
finer and finer fibres. I feel quite convinced, therefore, that 
the primitive fibres observed in the nerve-trunks of the cor- 
nea are not single fibres, as is generally believed, but com- 
pounded, of several finer fibres held together by that peculiar 
kind of connective tissue already spoken of. Dr. Beale has 
been led to conclusions of a similar kind from his observations 
upon the nerves distributed to the mucous membrane which 
covers the human epiglottis. 
It is well known that the opinion generally received as 
regards the nature of these primitive nerve-fibres, is that the 
nerves of the cornea contain fine dark-bordered primitive 
tubes 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^^ (Kblliker). In my own specimens 
such distinction is not observed. All the nerves, from the 
entrance into the cornea to their ultimate distribution, do not 
appear to contain any fibre which could properly be called dark- 
bordered. All the fibres exhibit the same appearance and 
refract the light in the same way. I have, amongst many 
others, a specimen in which all the nerve-fibres, from the 
margin of the cornea to their termination, have been so acted 
upon by acetic acid as to display a very remarkable granular 
appearance. With the purpose of ascertaining the chemical 
nature of these granules I have treated some specimens which 
