Nerves to the Skin of the Fi^og, 
25 
It is interesting to notice here a fact witli reference to tlie 
nerve-fibres of the capillary vessels^ which has very often 
fallen vv^ithin my observation ; that is, that several of those 
branches resulting from the repeated division of the fine 
bundles, which have left the sheath of the capillaries, after a 
more or less lengthened course, enter the sheath of some 
bundles of dark-bordered fibres. It is very probable that 
these fibres, after running for some distance in the same 
sheath with the dark-bordered fibres, leave the sheath at 
another point, and pass to their distribution. 
In short, the capillaries of the skin of the frog are largely 
supplied with nerves. In the finest arteries and the largest 
capillaries the nerve-fibres run parallel to and close by them ; 
but in the finest ones the nerve-fibres, after running with 
them for some distance, generally cross them and pass from 
one capillary to another. The nerve-fibres distributed to all 
capillaries are in connection with one another, so that they 
form a lax plexus which lies on different planes. 
4. Of the nature and origin of the fine nerve-fibre 's travelling 
in company ivith the dark-bordered fibres. 
I come now to the last and most difficult part of this paper. 
What is the nature and what is the origin of the fine nerve- 
fibres running in the same sheath with the dark-bordered 
fibres ? These two questions seem to be so linked together 
that, by the solution of the first, the second will be greatly 
facilitated. With regard to the first question I observe that 
there exists the most perfect similarity between the fine nerve- 
fibres just mentioned and those which accompany the capillary 
vessels ; in fact, both kinds of fibres have the same refractive 
power and are acted upon by acetic acid in the same w^ay. 
In both of them are found those characteristic spindle-shaped 
swellings which have been already spoken of. They very 
frequently unite with each other, and the fine fil^res which 
run in the same sheath wdth the dark-bordered fibres are seen 
very often to pass to the capillaries, and vice versa. Not 
only so, but the fact must be here noted, which I have fre- 
quently observed, viz., that when a large bundle of dark-bor- 
dered fibres happens to run close to a capillary for some dis- 
tance, after leaving it, the capillary is observed to be supplied 
with a greater number of nerve-fibres, than before. Hence 
it may reasonably be inferred that the greater part of the 
fine nerve-fibres which are seen in company with the capillary 
vessels at the periphery, are divided from those running in 
the same sheath with the dark-bordered fibres. 
