86 
CiACcio_, on the Nerves of the Cornea, 
presented sucli appearance with ether^ and liave found that 
some of the granules were readily dissolved by the ether_, 
while others resisted its action. The natural conclusion from 
this experiment is that the so-called non-medullated or pale 
nerve-fibres consists of fatty matter in combination Avith a 
protein compound. On being disintegrated by the action of 
acetic acid^ both assume the granular form. Nevertheless it 
must be borne in mind that^ although the pale nerve-fibres^ 
by the action of acetic acid^ pass through the change I have 
already mentioned_, yet they never lose their outlines^ which 
only become paler and indistinct. 
An alteration precisely resembling that which has been 
described is also efifected by acetic acid on the cornea-cor- 
puscles and their branching processes ; and the granules thus 
produced are acted upon by ether in the same way as those of 
the pale nerve-fibres. This I mention incidentally because 
I am not sure whether it has been noted by those who have 
purposely studied the subject. I believe that a comparative 
study (histological as well as chemical) of the cornea-cor- 
puscles would afford more positive information upon their 
nature than we now possess. Careful observations have shown 
that these corpuscles have not the same appearance and size 
in man, cat, and mouse_, as in the frog, eel, and sparrow. 
- I must not omit to say, finally, that the nerves distributed 
to the cornea of diff'erent animals are not of the same degree 
of firmness. I have found that in the sparrow, frog, mouse, 
man, and fishes, the firmness of the nerve-fibres decreases in 
the order in which I have mentioned the animals. It is not so 
easy, therefore, to make out the nerves in the cornea of man 
and fishes, because the nerve-fibres being extremely soft are 
so altered by the chemical agents which we are obliged to 
employ, that it is more difiicult to trace them among the 
other elements of the corneal tissue than in the other in- 
stances. 
Channels which contain the nerves running through the 
cornea. 
This question, as it seems to me, must be considered from 
two different points of view. If the term channels is here 
taken in the meaning of grooves or spaces excavated through 
the fibrous tissue of the cornea, where the nerves lie, the 
existence of such channels cannot be doubted. But if, on 
the contrary, the word is understood in the sense in which 
it is generally used, viz., as signifying tubes with distinct and 
proper walls, I strongly hold that, in this meaning, such 
