NERVOUS CENTRES. (Tuer Microscopicat Anatomy.) 
delirium which succeed to hemorrhages, large 
bleedings, or the sudden lighting up of inflam- 
-Mation in the pericardium or within the heart. 
In nearly all these cases, however, it is important 
to notice that the blood is more or less damaged 
in quality, deficient in some of its staminal 
principles, or charged with some morbid matter ; 
and this vitiated state of the vital fluid has no 
doubt a considerable share in the production of 
the morbid phenomena.* 
Of the encephalic nerves.—There are no com- 
mon characters possessed by these nerves, such 
as have been enumerated at a preceding page 
for the spinal nerves. They are, however, dis- 
pared in pairs, and are quite symmetrical. 
ith the exception of the olfactory, optic, and 
third pair, they are all connected with the 
mesocephale or medulla oblongata. 
The arrangement of these nerves originally 
proposed by Willis has been so long adopted 
in this country and on the continent that no 
advantage would arise from abandoning it, un- 
_ less some other of an unexceptionable nature 
could be substituted for it. It has, therefore, 
been followed in this work, and the anatomy 
and physiology of the encephalic nerves have 
been described in articles prefixed by their 
__ numerical titles, in all cases except the olfactory 
and optic, and the eighth pair of nerves. + 
Twelve pairs of nerves are found in con- 
nection with the base of the encephalon. Five 
pairs have been so classed by Willis as to form 
two in his arrangement, three pairs being al- 
lotted to his eighth pair of nerves, and two to 
his seventh. Willis’s arrangement, therefore, 
comprises nine pairs of nerves, which he 
enumerates, beginning at the anterior and pas- 
_ sing to the posterior part of the base of the 
brain. These are the first pair or olfactory 
nerves; the second pair or optic; the third 
_ pair, motores oculorum; the fourth pair,’ pa- 
 thetici ; the fifth pair; the sixth pair, abdu- 
_ centes oculi; the seventh pair, including the 
_ portio mollis or auditory nerve, and the portio 
_ dura or facial nerve; the eighth pair, including 
_ the glosso-pharyngeal, the pneumo-gastric, and 
the spinal accessory ; the ninth. pair or hypo- 
_ glossal. The first cervical nerve or the sub-occi- 
_ pital was considered by Willis as an encephalic 
nerve and counted as the tenth pair. 
As the cranium may be shewn to be com- 
ed of the elements of three vertebra, it 
been attempted to prove that among these 
nerves some may be classed with the vertebral 
_orspinal nerves. The fifth is obviously of this 
kind from its anatomical characters, namely, 
two roots; one, small, gauglionless ; the other 
large, ganglionic; but with the former, which 
is analogous to the anterior root of a spinal 
nerve, the third, fourth, and sixth nerves may 
be conjoined from their similarity in structure 
and distribution. Thus one cranio-vertebral 
————— 
* The subject of the circulation in the cranium 
has been very ably discussed by Dr. G. Burrows in 
the Lumleian Lectures for 1843, Lond. Med. Ga- 
zette, vol. xxxii. 
+ The olfactory nerve is described in the atricle 
NosE, the optic in OpTic Nerves, and the eighth 
pair under the titles of its three portions. 
707 
nerve is formed, the anterior root of which 
consists of the small portion of the fifth, the 
third, fourth, and sixth nerves; and the pos- 
terior or sensitive root, of the large portion of 
the fifth. A second cranio-vertebral nerve 
consists of the eighth pair, to which might be 
added the facial contributing to its motor por- 
tion; and a third is formed by the hypoglossal. 
The analogy, especially in the latter case, is far 
from being very obvious. 
Sketch of the microscopical anatomy of the 
spinal cord and brain.—We conclude our ac- 
count of the anatomy of the spinal cord and 
brain with a rapid glance at the present state 
of our knowledge of their minute anatomy as 
revealed by microscopical observation. 
The elements of the two kinds of nervous 
matter, fibrous and vesieular, have been al- 
ready sufficiently described. We shall only 
remark here that the great object of the ana- 
tomist’s research should be to find out the 
precise manner in which the nerve-fibres are 
united with the nerve-vesicles. Of their in- 
timate connection there can be no doubt,— 
much less of the influence which they are 
capable of exerting mutually upon each other.* 
Among the peculiarities of the fibrous mat- 
ter in the centres it may be here stated that 
the fibres pass through a much greater range of 
size than in the nerves, that here we meet with 
nerve-tubes of the largest size, and, on the other 
hand, with minute fibres which seem to be con- 
tinuous with the branching processes of the 
caudate nerve-vesicles. These fibres are per- 
fectly transparent and differ from the nerve-tubes 
in the absence of any ef the white substance of 
Schwann, and of the tubular membrane. 
Some idea of the relation of the vesicular 
and fibrous matter in different parts of the cere- 
bro-spinal centre may be formed by examining 
thin sections of the several portions of them 
made in various directions. It is impossible 
to make these sections sufficiently thin to enable 
us to explore a large surface with a high power, 
for which great transparency is necessary. Such 
sections, however, may be examined with low 
powers, as Stilling and Wallach have done. It 
1s important, however, to notice that the ap- 
pearances observed in this way afford no certain 
indication of the course and direction of the 
nerve-fibres, nor of the situation of the finer 
elements of the vesicular matter. The nerve- 
tubes are too minute to admit of being followed 
with an object-glass which magnifies less than 
from two hundred to three hundred diameters; 
yet Stilling’s researches have been made with a 
power of no more than ten or twelve diameters. 
The fibrous matter of the spinal cord consists 
of some fibres which pass either in a vertical 
direction, or obliquely, taking a long course, 
and deviating but slightly from the parallel to the 
axis of the cord. The fibres of the posterior 
columns are the most obviously longitudinal, 
and those which lie quite on the surface of the 
antero-lateral columns follow very much the 
same direction. Among the elements of the 
grey matter, fibres are found in great numbers, 
* See the article NERVE, and pp. 646, 7, et seqq. 
