Nerves to the Skin of the Frog. 
17! 
It is very remarkable^ that the dark-bordered fibre, a little 
before its division, is observed to contract abruptly and reduce 
itself into a subtile filament, which divides into two others 
of an equal size, and which sometimes gradually, but more 
frequently suddenly, swell up as to form two dark-bordered 
fibres much larger than the originary one. Less frequently, 
however, the dark-bordered fibre, without any previous con- 
traction, is seen to divide into two very fine fibres, which, 
shortly after, increase considerably in size. The appearances 
I have just described do not appear to me to be sufficiently 
explained in the doctrine at present generally received of 
the anatomical constitution of the primitive nerve-fibre. I 
must here add, that in preparations wherein very strong 
glycerine has been nsed, and through the medium of which 
the dark-bordered fibres are seen, these appear quite homo- 
genous, with a pearly brightness, and without the slightest 
indication of their three distinct structures. 
In connection with each dark-bordered fibre are observed, 
at irregular distances, several oval nuclei, which are deeply 
coloured by carmine, and generally equal in breadth to the 
fibre itself. Sometimes they seem to lie in the middle of the 
fibre, and sometimes at one of its sides. It is very probable 
that they are seated within the white substance of Schwann. 
These oval bodies, or nuclei, can be distinctly seen only in 
specimens which, after being stained in carmine solution, are 
kept in maceration for some time in strong glycerine, and then 
treated with glacial acetic acid. According to my observations 
the glacial acetic acid disintegrates the white substance, but 
has no influence on the nuclei, which become clearly visible. 
The bundles of the dark-bordered fibres Avhich, as I have 
stated, are distributed to the inner layer of the derma of the 
frog, do not accurately follow the capillary vessels in their 
course. True it is that some large bundles are seen running 
parallel with and close by the capillaries for some distance ; 
but, as a rule, the plane of distribution of the former, and 
that of the latter, are quite distinct. The bundles, during 
their course, divide more frequently in a dichotomous man- 
ner, but at times some of them are seen to divide into three 
or four smaller bundles, which pursue diff'erent courses. The 
division generally occurs at acute and, very rarely, at right 
angles. It is interesting to remark here that all the bundles, 
which result from the repeated division of the main ones, 
never loose their sheaths ; nay, it seems to me more conform- 
able to the truth to say that all the sheaths of the diff'erent 
bundles are immediately continuous with one another. 
While the bundles of the dark-bordered fibres, continually 
VOL. XII. b 
