600 
nerves both kinds of fibres may be found, but 
in the latter these peculiar fibres are enormously 
predominant, so that ,%,ths of their elements, or 
even a larger proportion, are composed of them ; 
in passing into neighbouring trunks they run as 
often centrad as to the periphery. When the 
Sympathetic fibres occur in cerebro-spinal 
nerves, they are collected into separate bun- 
dles. The nervous branches which go to the 
involuntary muscles contain almost exclusively 
the smaller or sympathetic fibres. Mucous 
membranes are almost exclusively supplied by 
these fibres. The viscera of the chest and ab- 
domen receive nerves which are made up 
almost exclusively of sympathetic fibres. 
These statements are quite at variance with 
the results of my observations, as well as of 
those of Henle and Pieqeee 
The authors remark a considerable difference 
as regards the relation which these peculiar 
fibres bear to the cerebro-spinal centres in 
Frogs, Mammalia, Birds, and Fishes. In 
frogs the fine fibres originate in greatest part 
from the ganglions on the posterior roots of 
Spinal nerves and from those of the sympa- 
thetic. In Mammalia the brain and spinal 
cord are not the only sources of the aeen etic 
fibres. The ganglia also probably give off some. 
In birds the ganglion of the vagus is a pro- 
bable source of sympathetic fibres; and in 
fishes the great thickness of the branches of the 
vagus, which are very rich in the fine fibres com- 
pared with the small size of its roots which are 
deficient in them, indicates that the 
ganglion of that nerve is a source of 
very numerous sympathetic fibres. 
e anatomical statements of these 
writers would, if founded in fact, go 
far to confirm the opinions of those 
physiologists who uphold the inde- 
pendence of the sympathetic system, 
and to prove the ganglia to be distinct 
centres of nervous influence. It is 
impossible to enter further upon the 
discussion of this question at present, 
without introducing physiological ar- 
guments. Ina subsequent part of the 
article we shall return to the subject.* 
Nerves of Invertebrata—In those Inverte- 
brata in which a definite arrangement of the 
nervous system has been made out, the same 
elements of the nervous matter are to be found 
as in the Vertebrata. The grey matter consists 
of globules with nuclei and nucleoli precisely 
like those of the human brain. From the gan- 
glia the nerves radiate ; the nerve-tubes, which 
are very delicate and transparent in the recent 
state, contain a soft pulpy matter easily altered 
by re-agents. They are themselves collected 
into bundles which are surrounded by a clear 
transparent membrane, of the same kind as 
the sarcolemma of muscle, which accompa- 
nies and surrounds the branches of the nerves. 
As the nerve-tubes separate from the primary 
trunk into smaller fascicles, these sheaths bi- 
furcate, so as to adapt themselves to the new 
branches. From the clear outline of the 
* Die Selbstandigkeit des sympatheschen Ner- 
vensystems, &c. von. Bidder und Volkmann. 
NERVOUS SYSTEM. (Nerve.) 
sheath, and the faintness and indistinctness of 
the margins of the nerve-tubes contained within 
it, this arrangement in the smaller nerves has 
very much the appearance of a bifurcation of the 
nerve-tubes themselves. There seems, however, — 
no reason to believe that the nerve-tubes of I 
vertebrata follow a different law from thatwhich 
regulates their disposition in the Vertebrate — 
series. It is likewise highly probable that the 
relations of these nerve-tubes to both periph ; 
and centre are essentially the same as in Ver. 
tebrata. Plexuses occur much more 
according to Valentin, in the nerves of 
tebrata. 
Of the developement of nerve-—We can add — 
nothing to the account given by Schwann of © 
the developement of nerve. The 
quoted from Wagner’s Physiology. 
“ The nerves appear to be formed 
the same manner as the muscles, viz. by the 
fusion of a number of primary cells a 1 
in rows into a secondary cell. The fp 
mary nervous cell, however, has not yet been 
seen with perfect precision, by reason of the 
difficulty of distinguishing nervous cells whilst 
yet in their primary state, from the indiffe 
cells out of which entire organs are evol 
When first a nerve can be distinguished as su 
it presents itself as a pale cord with a longi 
dinal fibrillation, and in this cord a multit) 
of nuclei are apparent. ( Fig. 335,a.) It is 
easy to detach individual filaments from a cor 
Fig. 335. 
4 
oad 
J 
of this kind, as the figure just refer 
shows, in the interior of which many n 
are included, similar to those of the primi 
muscular fasciculus, but at a greater distar 
from one another. The filaments are p. 
granulated, and (as appears by their fart 
developement) hollow. At this period, a 
muscle, a secondary deposit takes place u 
the inner aspect of the cell-membrane of 
secondary nervous cell. This secondary 
it is a fatty white-coloured substar 
it is through this that the nerve acquires 
opacity (fig. 335, 6). Superiorly the fibr 
still pale; inferiorly, the deposition of 
white substance has occurred, and its effeet 
remieing ry fibril dark is obvious. aoa 
advance of the secondary deposit, the fibr 
become so thick, that the double outline 
their parietes comes into view and they 
quire a tubular appearance (c). On the ¢ 
currence of this secondary deposit fhe nue 
of the cells are generally absorbed; yet a fe’ 
may still be found to remain in 
sy 
9 
for some- ti 
