4 
in size as they approach and enter the grey 
matter. 
Of the grey nervous matter.—The grey ner- 
vous matter differs very materially in its ana- 
tomical characters from the white. Its ele- 
ments are vesicles or cells, with nuclei and 
nucleoli. Although this vesicular or cell form 
is universally prevalent, the cells present much 
_ diversity of shape, size, and colour in different 
_ Centres or even in the same centre, which ap- 
parently have reference to some peculiarity 
of function. The most prevalent form is that 
of a globular vesicle, composed of a very deli- 
_ Cate transparent membrane. Within this mem- 
brane is contained a soft minutely granular sub- 
Stance, which forms the principal mass of the 
body, parenchymmasse (Valentin). The grey 
colour of the vesicle, which becomes very ma- 
nifest when a number of them is congregated 
together, is dependent on this granular matter. 
Gee fig.371, a,b,c.) When the vesicle bursts 
‘and its substance is broken up, the granular 
‘matter is diffused, and confuses and darkens 
the specimen under examination. Sometimes 
the outer vesicle is removed, the contained 
F: lar matter retaining the globular form. 
fithin the external vesicle (a, fig. 371) there 
Nerve vesicles from the Gasserian ganglion of the 
a human subject. ™ 
- @, a globular vesicle with defined border; 6, its 
nuc 3 ¢, its nucleolus; d, caudate vesicle; 
@, elongated vesicle with two groups of pigment 
ticles ; f, vesicle surrounded by its sheath or 
stile nucleated particles; g, the same, the 
ith only being in focus. 
is another much smaller and adherent to a 
art of its wall, so as to be quite out of the 
centre of the containing vesicle. This is the 
nucleus (6, fig. 371). Its structure is ap- 
parently of the same nature as that of the ex- 
é vesicle. The nucleus contains in its 
tre another minute and remarkably clear 
and brilliant body, also vesicular in structure. 
This is the nucleolus (c, fig. 371). Sometimes 
it is replaced by two or three much smaller 
but similar bodies. The softness of the vesicle 
admits of its yielding, whether from the dis- 
turbance occasioned in the necessary manipu- 
* Iam indebted to the accurate pencil of my 
Mr, Bowman for this illustration. 
NERVOUS CENTRES. (Human Anatomy. Grey Nervous Marrer). 
647 
lation or from the pressure of the neighbouring 
elementary parts as it lies in its proper situation. 
Hence it is that these vesicles exhibit a consi- 
derable diversity of form. 
Very frequently we observe that, besides the 
granular substance above described, there are 
certain pigment particles of large size and dark 
colour, which are collected into one or two 
roundish or oval groups, situate at or towards 
one or both sides of the vesicle (fig. 371, e). 
These masses of colouring matter sometimes 
occupy considerable space, and enable the ob- 
server readily to detect the position of such 
vesicles as contain them. hen the mass of 
pigment is placed at one side, we may com- 
pare the containing vesicle, as Volckmann has 
done, to a fruit which is coloured only on that 
side which is exposed to the sun. The aggre- 
gation of many such vesicles at any one spot 
gives the nervous matter there a peculiarly dark 
colour. A remarkable example of this is found 
in that portion of the crus cerebri which is 
known by the name of locus niger. 
A very interesting form of nerve-vesicle is 
that which exhibits the greatest departure from 
the globular shape by the prolongation of the 
wall of the outer cell into one or more tail-like 
processes. These bodies may, from this pecu- 
liar character, be designated caudate nerve- 
vesicles. They possess the nucleus and nucleo- 
lus, as in the more simple form, and contain 
one or more of the masses of colouring matter; 
indeed, in them the quantity of pigment is 
generally much more considerable than in any 
other form. I have noted an observation which 
shewed two nuclei in one vesicle. They vary 
much in size and shape, and so also do the 
processes. The largest nerve-vesicles are found 
among those of this description. The variety 
in shape may depend in some degree upon the 
situations from which the caudate processes 
take their rise. In some (fig. 371, d) they 
proceed from opposite poles of the vesicles; 
in others they arise near each other from the 
same region of the vesicle, and when numerous, 
give to it somewhat the form of a cuttle-fish 
with extended tentacles. In examining the 
structure of one of these processes, we find it 
evidently exactly similar to that of the matter 
contained in the outer vesicle, exhibiting the 
saine minutely granular appearance. The pro- 
cesses are implanted in the surrounding sub- 
stance, and firmly connected with it, so as to be 
with great difficulty separated from it. They 
exhibit much strength of cohesion, but are fre- 
quently broken off quite close to their points 
of origin, and the broken ends present a dis- 
tinctly lacerated edge (d, fig. 371). More 
rarely we are able to trace these processes to 
a considerable distance, and then we observe 
them to bifureate or even to subdivide further, 
and to terminate in exceedingly fine transpa- 
rent fibres, the connexion of which with the 
other elements of the nervous matter has not 
yet been ascertained.* 
* See a beautiful illustration of one of the largest 
of these vesicles in the second part of Mr. Bowman’s 
and my work on Physiological Anatomy and 
Physiology. 
