648 
It is in vain, in the present state of our 
knowledge, to speculate upon the use of these 
caudate processes. Do they constitute a bond 
of union between the nerve-vesicles and certain 
nerve-tubes? or are they commissural fibres 
serving to connect the grey substance of different 
portions of the nervous centres? Until a more 
extended research has made us better acquainted 
with the peculiarities of these vesicles in various 
localities, it would be premature to offer any 
conjecture concerning their precise relation to 
the other elements of the nervous centres. They 
exist, with different degrees of developement, 
in the locus niger of the crus cerebri, in the 
lamine of the cerebellum, in the grey matter 
of the spinal cord and medulla oblongata, and 
in the ganglions, and in the grey substance of 
the cerebral convolutions, in which latter situa- 
tion they are generally of small size. 
When a portion of grey matter from a con- 
volution of the brain is examined with a high 
power in the microscope, we observe it to con- 
sist chiefly of a mass of granular matter, in 
which nerve-vesicles are imbedded with consi- 
derable intervals between them. Henle states, 
with much truth, that the superficial part of the 
grey matter of the convolutions seems almost 
entirely composed of finely granular substance, 
in which lie, scattered here and there, several 
clear vesicles which, as he remarks, look almost 
like openings (fig. 372). In the middle por- 
tion the vesicles appear larger, and the gra- 
nular matter becomes less abundant, and on 
the most deep-seated plane the nerve-vesicles 
are much increased in size and lie in closer 
juxtaposition, being, however, covered by a 
thin layer of granular matter, which forms a 
sheath to each vesicle. Nerve-tubes are found 
throughout the whole depth of the grey matter. 
Those in the most superficial layer are ex- 
tremely fine and varicose, and seem to corre- 
spond in number and situation to the vesicles. 
For wherever there is a nerve-vesicle, we find an 
extremely fine varicose nerve-tube apparently 
adherent to it. 
Fig. 372. 
Grey substance from the surface of the cerebral hemi- 
sphere of a full-grown rabbit treated with dilute 
acetic acid. (After Henle. ) 
a, nerve-vesicle ; b, a similar one with two nu- 
clei; c, another viewed along its edge ; d, vesicles 
indistinctly apparent ; e, granular matter. 
In the grey matter of the ganglions we find 
that the vesicles are also deposited in granular 
matter, which surrounds each of them as a 
sheath (fig. 371, f, g), completely investing it 
NERVOUS SYSTEM. (Neavous Cextres Grey Nervous Mattern) 
on every side, and separating it from the neigh- 
Satine nse. Here, however, the sheath is 
formed not only of a finely granular matter, but 
also of numerous bodies which resemble nucle 
or cytoblasts, and this sheath invests both th 
globular variety of nerve-vesicles and the cau- 
date ones. Nerve-tubes lie in immediate con. 
nexion with these vesicles, and sometimes en- 
twine themselves around them, and seem te 
indent their sheaths (fig. 375.) . 
Other vesicles, much more simple in form, are 
found in the grey matter in certain situations, 
The outer layer of the optic thalamus, accord= 
ing to Henle, contains only small homoge 
neous globules, analogous to the nuclei of the 
ganglionic globules, in immediate appositior 
with each other, and towards which the tuk 
seem to ascend in the vertical direction. Pure 
kinje states, that a similar layer is met with in 
the cortical substance of the brain quite close 
to the medullary substance.* I find a lays 
of similar particles in the grey matter of 
cerebellic lamine. And, according to 
report of Valentin,+ Purkinje has found 
inteior of the ventricles in the normal s 
covered by an oily matter, which consis 
of distinct, large, transparent globules, ff 
and lying near each other. A similar lay 
has been found by him in the interior of t 
fifth ventricle. The cavity of the rhomboi 
sinus in Birds likewise contains a gelatino 
mass, which consists of large globules lyi 
close to each other. { ; " 
Developement of grey matter —In the 
fect nerve-vesicle, the cell form of primi 
developement is persistent. We have the 
cleolus and nucleus (cytoblast) and the ce 
and, according to Schwann, the only cha 
which the full-grown cell exhibits consists i 
increase of size and in the developement of) 
igmentary granules within. The following” 
alentin’s description of the developemen 
nerve-vesicle. In the very young embryo 
Mammalia, as the sheep or calf, the cen 
mass in the course of formation contains, if 
midst of a liquid and transparent blas 
transparent cells, with a reddish yellow nue 
The wall of the cells is very thin and sit 
their contents are colourless, transparent 
mogeneous, and manifestly liquid; the nut 
with well-defined contour, is general! 
sometimes central, at other times exe 
solid, and nearly of the same colour 
corpuscles of the blood. Around these 
tive cells of the central nervous system, 
we find likewise formed after the same 
the spinal cord, a finely granular mass bee 
deposited, which probably is not at fi 
rounded by an enveloping cell-membra 
this early period of formation the prin 
still preserves its first delicacy to such a 
that the action of water causes it to bu 
mediately. This rupture of its membrane 
effusion of its contents often take place st 
denly and quickly that they can per 
* Henle, loc. cit. t Uber den Verlauf, 
¢ See further remarks on the grey ma 
account of the minute structure of the br 
spinal cord in a subsequent part of the artic 
da 
