650 
Fig. 373. 
Pn 
ASW gy — \ 
i/ 
Fa 
-_ 
Second abdominal ganglion of a greenfinch, slightly 
compressed under the compressor. The course of the 
nerve-tubes only is represented. 
a, fibres passing in ; 6, emerging fibres; c, sur- 
rounding fibres. ‘The meshes for the reception of 
ganglion globules are shown. 
Fig. 374. 
A small piece of the otic ganglion of the sheep, slightly 
compressed, ow the interlacement of the Score 
nal fibres and the grey matter. 
(After Valentin. ) 
tin, travel round the margin of the ganglion, 
and to these he gives the name of umspinnende 
Fasern, surrounding fibres, and some fibres 
from them to the more central ones, or 
fom the latter to the former. Nerve-vesicles 
exist at the circumference of the ganglion as 
well as in its interior, and to them is due the 
peculiar grey colour of that body. 
The best mode of examining these points is 
to select the smallest ganglia of very small 
animals, birds, mice, &c.; these, when sub- 
jected to compression, become very transpa- 
rent, and display much of their intrinsic ar- 
rangement. Or thin slices of large ganglia may 
be placed under the microscope, and when torn 
up by needles the disposition of the nerve- 
vesicles and the caudate processes, when pre- 
sent, are rendered visible. And none is more 
suitable for this ees than the Casserian 
ganglion of the fifth nerve, which by the ab- 
sence of a dense sheath and its greater loose- 
ness of texture is more easily examined. 
It is a highly important problem, in minute 
NERVOUS SYSTEM. (Nervous Centres. Tue Sprvat Corp.) 
anatomy, to determine whether there are any 
nerve-tubes which terminate in the grey matter: 
the ganglion, or originate in it,—which in 
are not continued through the ganglion. 
present we are unable to state further than the 
the tubes appear to have an intimate connect 
with the nerve-vesicles wherever the latter 
be found, and that they often appear to be col 
tinuous with the sheaths of the nerve-vesic! 
Nerve vesicles from the Gasserian ganglion covered 
their sheaths of nucleated particles, to shew the u 
mate relation of the nerve-tubes to them. 
t, t, nerve-tubes; v, v, vesicles. 
There does not ap to be any mate 
difference of structure between the ganglion: 
the sympathetic and those of the cereb 
system, excepting, as Henle states, the ex 
ence of a greater number of gelatinous 
in the former. a 
Of the cerebro-spinal centre.—The nerve 
mass which occupies the cavities of the 
nium and spine doubtless constitutes ¢ 
centre, as there is a perfect continuity thro 
out all its . But the differences of ext 
form and characters in some regions of it, 
the obvious diversity of endowment of the née 
connected with certain portions, denote — 
justify an anatomical as well as a physiolo 
subdivision of it into segments, each of ¥ 
is a centre of nervous action independent ¢ 
rest, yet so connected with them that the 
tions of all are made to harmonize in the 
perfect manner. 
The subdivision which the external an 
indicates, although not perfectly coineid 
that which the differences o i 
suggest, has been so long sanctioned by 
and is so convenient for description, — 
advantage would be gained by ade tin 
other, Our description of the ¢ 
centre, or axis as it has also been caller 
be given under the following ds: 
spinal cord; 2. the encephalon, includin 
medulla oblongata; 6, the mesoceph 
cerebellum; d, the cerebrum. 
1. Or THE sPiNaL cornp.—Syn. Spin 
row, Medulla spinalis; Fr. La moé ee 
Germ. Das Riickenmark. The follo 
the anatomical limits which may be a 
the spinal cord. It occupies a large 
the spinal canal, terminating inferiorl 
point which, in different subjects, rang 
tween the last dorsal and the second 
vertebra. Below this point the sheath fo 
by the dura mater contains leas 
nerves which is called the cauda equim 
a 
ae 
