NERVOUS CENTRES. (HUMAN ANATOMY. GRE\ NERVOUS MATTER). 647 



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, parenchymmaxse (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. 

 (See Jig. 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 

 granular matter retaining the globular form. 

 Within the external vesicle (a, Jig. 371) there 



Fig. 371* 



Nerve vesicles from the Gasserian ganglion of the 



human subject. 



a, a globular vesicle with defined border; b, its 

 nucleus ; c, its nucleolus ; d, caudate vesicle ; 

 e, elongated vesicle with two groups of pigment 

 particles ; /, vesicle surrounded by its sheath or 

 capsule of nucleated particles ; g, the same, the 

 sheath only being in focus. 



is another much smaller and adherent to a 

 part of its wall, so as to be quite out of the 

 centre of the containing vesicle. This is the 

 nucleus (b, Jig. 371). Its structure is ap- 

 parently of the same nature as that of the ex- 

 ternal vesicle. The nucleus contains in its 

 centre 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- 



* I am indebted to the accurate pencil of my 

 friend Mr. liowuian for this illustration. 



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 (Jig. 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. When 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 (Jig. 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 

 same 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, Jig. 371). More 

 rarely we are able to trace these processes to 

 a considerable distance, and then we observe 

 them to bifurcate 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. 



