654 
and the matter, and remarkable varieties 
as regards shape of the lateral portions of 
the latter. The relative proportion of the grey 
matter to the white appears to be much greater 
in the lumbar than in the cervical or dorsal 
regions. In the upper part of the cord the 
crescentic portions are narrow, and the white 
matter is abundant. The posterior horn a 
pears as a thin lamella extending back to the 
surface, while the anterior is a small, roundish, 
slightly stellate mass, remote from the sutface 
of the anterior columns. In the dorsal region 
the grey matter is at its minimum of develope- 
ment: here it appears much contracted and 
diminished in size, although presenting the 
same general form as that in the region of the 
neck. In the lumbar region both horns acquire 
a manifest increase of thickness, the terior 
still extending back quite to the surface, and 
the anterior, more stellate than in the higher 
parts of the cord, separated from the corre- 
sponding surface of the cord by a much 
smaller quantity of white substance. At a 
still lower part of the cord, where the lumbar 
swelling begins to diminish in size, the pos- 
terior horn is short and thick, and some- 
times seems not to reach quite back to the 
surface of the cord,—an appearance, however, 
which might be produced by some accidental 
obliquity of the section; and its posterior 
extremity has somewhat of the form of a 
hook, its hindermost portion being directed 
a little forwards and inwards, forming a very 
sharp angle with the rest of the grey sub- 
stance which constitutes the horn. At the 
lowest part of the cord the crescentic form of 
the lateral portions of grey matter ceases, and 
the transverse section of it presents the form of 
a solid cylinder slightly notched on each side, 
and surrounded completely by the white sub- 
stance. ( Fig. 377.) 
There are also differences deserving of notice 
as regards the white substance in the different 
regions of the cord. The largest quantity of 
white substance is found in the cervical en- 
largement, as may be shown on a transverse 
section. Both the antero-lateral and the pos- 
terior columns are large, but by far the greatest 
 sapamtte of the mass of white substance must 
assigned to the antero-lateral columns. It 
is also important to remark that the quantity of 
white substance which is placed between the 
posterior horns in a great part of the cervical 
region is augmented by the existence of two 
small columns of white matter, which will be 
more particularly described when we come 
to speak of the medulla oblongata. These 
columns extend from the inferior extremity of 
the fourth ventricle, very nearly as far down 
as the termination of the cervical enlarge- 
ment, where they gradually taper to a fine 
point and disappear, allowing the posterior 
columns of the cord to come into apposition 
along the posterior fissure. These small co- 
lumns, the posterior pyramids of some authors, 
do not appear to be completely isolated from 
the proper posterior columns of the cord. There 
is generally a very clear line of demarcation 
between them, visible on the posterior surface, 
NERVOUS SYSTEM. (Nervous Centres. Tue Sprxat Corp.) 
Fig. 377. 
A 
ts 
= 
-s-@ 9OO@ 80-2 
- 
~ 
ce 
ie 
c 
' 
> 
Lis 
> Ot 
545 
' 
Transverse sections of are small; the 
inal cord. 
Arnold. ) 
the 
( After 
1, cervical region at 
the upper part of 
the swelling. 
2, the same at the tionally to the oth 
largest part of the 
swelling. 
3, dorsal region. 
4, lumbar region. 
5, pointed extremity. 
A, anterior surface, 
P, posterior surface. 
the posterior columns than u 
antero-lateral ones. 
‘the cord the white matter has gradually 
peared, and in the 
minal filiform process 
sent, according to Remak and Valentin. 
These facts lead to some interesting p 
logical conclusions bearing upon the 
of the cord as well 
in the upper extremities that volu ntary 
and sensibility are in their most highly 
loped state, and accordingly the size « 
portion of the cord from which the ne 
these parts emanate is greater than au 
portion of the cord. 
pendent on the grey matter or upon the 
terior columns, as has been conjectur 
by a distinct depression or 
fissure which n th 
length of the cord; bi 
this fissure does not exten 
much deeper than the su 
face, nor does any distin 
process er: mater sin 
into it. Nevertheless, i 
the spinal cord, which hi 
been hardened in aleohe 
or by any other chemic 
reagent, these columns w 
readily by te 
in the longitudinal dire 
tion, both from each oth 
and from the posteric 
columns between whi 
they are placed. Th 
occupy rather less 
one-half of the interval 
tween the posterior roots: 
the nerves, ppting 
their lowest part, 
from their ing 
they obviously take 
much less space. 
ao the dorsal regi 
th white and n 
ter are small pa it 
the posterior columns, hot 
ever, do not appear to € 
perience a diminution — 
size at all commensur 
with the general shrini 
of the organ in this regi 
nor with the reduced : 
of the antero-latera 
lumns. 
In the lumbar 
the antero-lateral colui 
of 
a 
is large in quantity, am 
the posterior columns 
pear to retain their s 
they are, indeed, 
of the cord, larger in 
than in the cervical 
and the — 
appears to depend © 
more upon the large 
of the grey matter: 
the k 
At the lowest 
- 
commencement of t 
grey matter only; 
as of its colanil 
Were the 
