DR. BEALE, ON NERVE-FIBRES. 15 
small arteries and veins also form networks, and very fine 
fibres can be traced ramifying amongst the muscular fibre- 
cells on different planes. Kdlliker suggests that ‘such fibres 
ramifying on the outer part of small arteries and veins dis- 
tributed to voluntary muscle, and on fine vessels on the arterial 
side of capillaries destitute of a muscular coat, are of the sen- 
tient kind. The latter fibres are probably afferent or sentient, 
but Kolliker’s remarks on this question are very undecided, 
and he does not profess to have studied the subject carefully. 
It is very hard to conceive what purpose could be served by 
the free distribution of sentient fibres upon and in the sub- 
stance of the muscular coat of an artery. Some of the fibres 
running with vessels distributed to voluntary muscles are cer- 
tainly motor branches, for, after running parallel with vessels 
for some distance, they diverge and are distributed to the 
muscular fibres. Kolliker considers certain nerves for the 
most part on the surface of the muscle as sentient fibres, but 
he adduces no facts which show that this view is correct.* 
It is important to state definitely that the bundles of very 
fine fibres, distributed to the frog’s bladder and in other tis- 
sues, are not visible in specimens prepared in the ordinary 
manner and examined in water or weak glycerine. In the 
bladder from which the specimen figured in No. xiii of the 
‘ Archives,’ plate I, was taken, there was no appearance 
whatever of these very fine fibres when the specimen was first 
prepared, but after the prolonged action of dilute acetic acid, 
a great number of bundles, many of which were as much as 
sosoth of an inch in diameter, and very many finer compound 
fibres, made their appearance. The vast majority of these bun- 
dles of fine fibres were not only destitute of true dark- 
bordered fibres, but of any one fibre more than the =5,4,;th of 
an inch in diameter. 
It is scarcely probable that any observer will doubt 
that the fibres figured are true nerve-fibres. Their mode of 
arrangement, the manner in which the trunks branch and 
ramify amongst the muscular fibre-cells, the character of the 
nuclei connected with the fibres, and the change produced in 
them by the action of acetic acid, show them to be nerve-fibres. 
The author has already proved that very fiue fibres invariably 
form the continuation of dark-bordered fibres, and that fibres, 
as fine as some of the finest of these, ramify in the same 
sheath with the dark-bordered fibre, even in the case of the 
dark-bordered fibres distributed to voluntary muscle (‘ Phil. 
Trans.’ 1862). 
But that thesevery finefibres in the bladder, which the author 
* “Croonian Lecture,” ‘ Proceedings of the Royal Society,’ 1862. 
