CHAP. VIII.] 



THE NERVOUS CENTRES. 



225 



of interlacement of the fibres thus takes Fig - 63 - 



place within the ganglion, and in its 

 interstices are lodged the nerve-vesi- 

 cles enveloped by their proper sheaths. 

 A great number of nerve-fibres may 

 be traced through the ganglion, so 

 that the emerging nerves may be re- 

 garded as resulting from a new com- 

 bination of the fibres that compose 

 the nerves which entered the ganglion. 

 These, however, are possibly not the 

 only constituent fibres of the emerging 



. _ , . , A small piece of the otic ganglion of the 



nerves, tor it has yet tO be ascertained, sheep, slightly compressed; shewing the 



, * IT- interlacement of the internal fibres, and 



Whether SOme fibres may UOt take their the vesicular matter. (After Valentin). 



rise from the vesicular matter of the 



ganglion, and it is a not less interesting object of inquiry whether 

 some of the entering fibres may not terminate in it. That the 

 nerve-tubes have an intimate connexion with the elements of the 

 vesicular matter is apparent, from the fact that they lie in close 

 apposition with them, and appear to indent their sheaths of nucle- 

 ated corpuscles (fig. 57). Sometimes the sheath seems to taper off 

 from the nerve-vesicles, and to become continuous with the nerve- 

 tubes. It is a conjecture by no means devoid of probability, that 

 the processes of the caudate vesicle may, after passing some way, 

 become invested by the tubular membrane and by the white sub- 

 stance of Schwann, and we have seen some appearances to warrant 

 this view (see fig. 56, c, d). Yet it should be stated, as opposed to 

 this view, that in the gray matter of the cerebellum the caudate 

 vesicles are so placed that their processes pass toward the free 

 surface of the cortical layer, and not into the white matter. 



Besides the tubular fibres, the ganglia contain likewise gelatinous 

 ones, which, however, are more abundant in the sympathetic than in 

 the cerebro-spinal ganglia (fig. 58, g). These fibres are, doubtless, 

 continuous with those of the same kind which may exist in the 

 entering or emerging nerves. We may also add, that the vesicular 

 matter does not appear to be confined to the interstices between 

 the fibres, but is likewise . found at the surface of the ganglia, 

 lying in immediate contact with their investing tunic. 



In the brain and spinal cord, there is a greater separation of the 

 vesicular and fibrous matter than in the ganglia. The former very 

 complicated organ, indeed, consists of various masses which are in 

 all essential points very similar to the ganglia in structure, and 



VOL. i. Q 



