598 
and therefore have been classed among the 
nervi molles by auatomists. In its peripheral 
distribution this nerve is prone to attach itself 
to the coats of bloodvessels, so much so, in 
fact, as to give it the character of an arterial 
or venous nerve; for, with a very few exceptions, 
it is always conveyed to o along the 
bloodvessels which are distributed to them. 
In its distribution it is entirely or almost con- 
fined to the trunk, and probably has no con- 
nexion with the extremities; or, if it have,that 
connexion must be by very few fibres, and 
those attached exclusively to the larger trunks 
of bluodvessels. The peripheral ramifications 
of this nerve are always plexiform, and being 
distributed on some non-symmetrical parts, 
the plexuses which are derived from opposite 
sides of the body meet and anastomose along 
the mesial plane. The solar plexus, for example, 
derives filaments from the right and left trunks 
of the sympathetic, and the plexuses which 
accompany the superior and inferior mesenteric 
arteries, are also supplied from each side. Of 
the precise nature of these plexuses nothing is 
known: it is obvious, however, that their me- 
dian anastomoses constitute a very peculiar 
feature, which strikingly distinguishes the sym- 
pathetic from the cerebro-spinal nerves, which 
do not anastomose along the mesial line. If in 
these anastomoses the looped arrangement exist, 
it might be conjectured to form a commissural 
connection between opposite and symmetrical 
portions of the sympathetic or of the brain or 
spinal cord. 
To determine the independence of this por- 
tion of the nervous system on the brain and 
spinal cord, it would be necessary to shew 
either that it possessed peculiar fibres distinct in 
characters from the cerebro-spinal fibres, which 
originated in the ganglia, and were occasion- 
ally bound up with cerebro-spinal nerves, or 
that fibres belonging to the ganglionic nerves, 
although exhibiting no essential difference from 
the cerebro-spinal, had their origin from the gan- 
glia and not from the brain or spinal cord. The 
present state of the investigations into this sub- 
ject does not enable us to determine these 
points; but there can be no doubt that at least 
a large proportion of the fibres which compose 
the sympathetic exhibit no essential difference 
from those of the cerebro-spinal nerves. 
When a portion of a sympathetic nerve is 
examined under the microscope, it is found to 
contain an unusually large quantity of white 
fibrous tissue, the fibres of which are arranged 
longitudinally. Crossing these are some fine 
circular fibres (of yellow elastic tissue) which 
are placed at some distance apart from each 
other. When the nerve is torn up by needles, 
numerous small oval cells may be seen among 
the fibres, their long axes being parallel to the 
fibres; these cells become much more visible 
when the fibrous tissue has been acted upon by 
acetic acid. They are scattered among the other 
elements of the nerve, and are probably persis- 
tent nuclei of the same kind as those which 
exist in muscle and other tissues. Numerous 
nerve-tubes are also seen entering into the for- 
mation of these nerves. These tubes appear 
to correspond in structure exactly with those 
NERVOUS SYSTEM. (Nenve.) 
of the cerebro-spinal system; they present th 
same clear outline, and contain a semifluid — 
pulpy matter, which is acted upon ina similar — 
way by reagents as that in the nerve-tubes i 
the cerebro-spinal system. They resemble, 
however, the nerve-tubes of the brain or spinal 
cord more than those of nerves, for they re 
much smaller and more delicate than the latter, 
and more prone to form varicosities. lie 
side by side of each other as in other ne 
and do not inosculate. The number of these 
nerve-tubes seems to vary in different parts of 
the sympathetic, apparently without regard to 
the size of the nerve, so that a small nerve m 
contain several nerve-tubes, while a large ont 
contains but a few. In the abdominal ramifi- 
cations the nerve-tubes are very numerous, 
also in the cardiac nerves, while the pa- 
thetic trunk in the neck contains but a few, which — 
are situated quite in the centre of the nerve. 
So far all observers appear to agree in the 
statements respecting the elementary compost 
tion of this nerve, and so far its intimate 
structure justifies the opinion that in its fum 
tions it must be intimately connected with 
cerebro-spinal nerves. A coarser anatomy 
already taught us that this nerve has extensi 
communications with the cerebro-spinal 
with all the encephalic nerves, excepting t 
of pure sense, and with all the spinal nerve 
by their anterior and posterior roots. It i 
now evident from microscopic observation th 
the object of these communications must be’ 
enable cerebro-spinal nerve-tubes to pass il 
the sympathetic system; and, in 
these communications may be 5 
many origins of the sympathetic from the bra 
and spinal cord. , 
It remains to inquire whether there is ar 
good foundation for the doctrine that the sy 
pathetic nerve contains distinct and peculi 
fibres, (grey fibres of some authors, 
independent of the brain and spinal cord, ; 
which by anastomosing with cerebral or sp 
nerves may confer upon them, to a certain ext 
the peculiar endowment which is supposed 
characterise the nerves of the former kind. — 
Retzius and Miiller appear to have bee! 
first to put forward distinctly the opinion 
certain cerebro-spinal nerves received 
cular fibres from the sympathetic, as the! 
received filaments from the former. 
Miiller* suggested that both the ganglionit 
the cerebro-spinal nerves should be k 
upon as compound in structure; “ 
ganglionic nerves contain motor, sensitive 
organic fibres, of which the latter kind % 
have the power of regulating the veg 
processes, and have a special relation 
ganglia; that the cerebro-spinal ne’ 
likewise com of motor, sensitive 
organic fibres, of which those of each 
have their specific destination, and run- 
course together without uniting with the 
that the ganglionic nerve consequently’ 
only in having numerous ganglia, and im 
taining a large number of grey fibres, - 
give it a proportionally greyer colour; W 
* 
* Miiller’s Physiology, by Baly, p. 710, 
