VESICULAR NERVOUS TISSUE. 



209 



113. 



245. The second primary element of the Nervous system, without which 

 the fibrous portion would seem to be totally inoperative, is composed of nu- 

 cleated cells, consisting of a finely granular substance, and lying somewhat 

 loosely in the midst of a minute plexus of blood-vessels. Their original form 

 may be regarded as globular ; whence they have been called ganglion-globules. 

 This, however, is liable to alteration; sometimes, perhaps, from external com- 

 pression ; but more commonly through their own irregular mode of growth. 

 They frequently extend themselves into long processes, which may give 

 them (according to the number thus projecting) a caudate or a stellate aspect, 

 resembling that of the pigment-cells of the Batrachia. These processes are 

 composed of a finely-granular substance, resembling that of the interior of the 

 vesicle, with which they seem to be distinctly continuous. They are very 

 liable to break off near the vesicle ; but if traced to a distance, they are found 

 to divide and subdivide, and at last to 



give off some extremely fine transpa- 

 rent fibres ; some of which seem to in- 

 terlace with those of other stellate cells, 

 whilst others become continuous with 

 the axis-cylinders of the nerve-tubes. 

 Such vesicles have been seen alike in 

 the ganglionic masses of the Cerebro- 

 spinal, and in those of the Sympathetic 

 system.* Besides the finely-granular 

 substance just mentioned, these cells 

 usually contain a collection of pigment- 

 granules, which especially cluster round 

 the nuclei, and give them a reddish or 

 yellowish-brown colour. This pigment 

 seems to have some resemblance to 

 the haematine of the blood ; and it is 



Usually, if not invariably, deficient 



among the Invertebrata, as well as less 

 abundant in Reptiles and Fishes. The 

 vesicles are sometimes covered with a 

 layer of a soft granular substance, which adheres closely to their exterior and 

 to their processes ; this is the case in the outer part of the cortical substance 

 of the human brain. In other instances, each cell is inclosed in a distinct en- 

 velope composed of smaller cells, closely adherent to each other, and to the 

 contained cell ; such an arrangement is common in the smaller ganglia, and 

 in the inner portion of the cortical substance of the brain. The diameter of 

 the vesicles is extremely variable, owing to the changes of form above de- 

 scribed ; that of the globular ones is usually between l-300th and l-1250th of 

 an inch. 



246. In the central or ganglionic masses of the Nervous system, we find 

 these vesicles aggregated together, and imbedded in a finely-granular matter; 

 the whole being traversed by a minute plexus of capillary blood-vessels. 

 The entire substance, made up of these distinct elements, is commonly known 

 as the cineritious or cortical substance ; being distinguished by its colour, in 



fibres, but to be a form of simple fibrous tissue. The peculiar fibres described above, were 

 first pointed out by Bidder and Volkmann; whose statements in regard to them have re- 

 cently been confirmed by the laborious anil impartial researches of Kiilliker. (See his work 

 "Die Selbstiindigkeit und Abhangigkeit des Sympathischen Nervensystems," 1844; and the 

 abstract of his results in Mr. Paget's able Report, in Brit, and For. Med. Review, July, 1840, 

 p. 271.) 



: See Todd and Bowman's Physiological Anatomy, Vol. i., p. 214. See also Kfllliker, loc. 

 cit.; and Dr. Radclyffe Hall, in Edinburgh Med. & Stirg. Journal, April, 1S46. 



13* 



Nerve-vesicles from the Gasserian ganglion of 

 the human subject : a. A globular one with de- 

 fined border; 6, its nucleus; c, its nucleolus. rf. 

 Caudate vesicle, e. Elongated vesicle, with two 

 groups of pigment particles, f. Vesicle surround- 

 ed by its sheath, or capsule, of nucleated panicles. 

 g. The same, the sheath only being in focus. 

 Magnified 31)0 diameters.] 



