SYMPATHETIC NERVE. 



431 



much as the ganglionic corpuscles are not dis- 

 tributed throughout the whole extent of the 

 nerve, but are confined to certain limited parts. 

 Remak believed it to be due to the presence of 

 structures termed by him organic nerve fibres : 

 Volkmann and Bidder also believed it to be 

 owing to a peculiar set of fibres, different, 



281. 



1. Tubular nerve-fibres from the thoracic portion of 

 the sympathetic cord in Man. 



2. Fibres of Remak (gelatinous fibres) and fine tubular 

 nerve-fibres, from the nerves of the spleen in the 

 Sheep. 



however, from those of Remak. Whether it 

 be due to the fibres of Remak or not, it seems 

 to be, at least, best marked in those branches 

 of the sympathetic in which these fibres are 

 most abundant. The sympathetic also differs 

 from the cerebro-spinal nerves in consistence 

 as well as in its appearance, being much softer 

 and more readily torn across than the latter. 

 This may be partly due to the want of the 

 strong distinct fibrous sheath possessed by the 

 latter, and partly also to a difference in the 

 character of the nerve fibres themselves. The 

 nerve fibres of the sympathetic are moreover 

 not arranged into distinct fasciculi, but lie 

 together imbedded in a mass of fibrous tissue 

 which accompanies them, serving the purpose 

 of a sheath. 



As regards the constituents of the sympa- 

 thetic nervous trunk, when a portion of one 

 of the main cords is examined with a power 

 of 250 diameters, it is found to be composed 

 of the following elements: 1st. Tubular nerve 

 fibres ; 2nd. Structures which present a homo- 

 geneous flattened appearance, and contain a 

 number of oval nuclei imbedded in them at 

 intervals ; and, 3rd. a quantity of white fibrous 

 tissue. 



The tubular nerve fibres which are present 

 in the sympathetic, differ much in point of 

 breadth from one another. Some of them 

 measure about -^-^ to ^^ of an inch in 

 diameter : their contents present the arrange- 

 ment of double contour and axis cylinder 

 which characterise the fibres occurring in the 

 eerebro-spinal nerves. Besides these fibres 

 there are others present which have also the 

 character of the tubular fibre, but are much 

 finer, measuring only from the ^gV<j to 



4-sVo- f an inch. They present distinct 

 margins, but have a paler aspect than the 

 above, and do not possess the double contour 

 which is seen in the broader tubular fibres, 

 and many of them often have a tendency to 

 the formation of varicosities. When running 

 in bundles they have, according to Volkmann* 

 and Bidder, who first called attention to their 

 anatomical characters, a yellowish grey hue 

 instead of the white pearly aspect of the 

 cerebro-spinal nerves. Sometimes the two 

 sets of fibres are intermingled and run side by 

 side with each other, at other times they run 

 in bundles more or less distinctly separated. 

 The number of fine fibres which are present 

 much exceeds that of the broader or coarser 

 variety. The two classes of fibres do not, how- 

 ever, appear to be distinctly marked off from 

 one another, there being present fibres which 

 possess partly the characters of the one and 

 partly those of the other. When one of the 

 finer variety is examined at the same time with 

 one of the coarser variety, and the two com- 

 pared, the points of distinction are sufficiently 



Fig. 28?. 



Broader, or animal, and finer, or sympathetic, pri- 

 mitive nerve-fibres, from tlte common trunk of the 

 vagus in the Frog. (Bidder and l'olkmann.~) 



marked, but a gradual transition from the fibres 

 belonging to the one set to those belonging to 

 the other may, in some parts of the sympa- 

 thetic, generally be traced. The finer the 

 nerve tubules are, the less distinctly do their 

 contents appear to be separated into central 

 portion or axis cylinder, and white substance 

 of Schwann. 



2. In regard to the structures No. 2. which 

 have been mentioned as occurring in the sym- 

 pathetic, Remak-}-, their discoverer, desciibes 



* Die Selbstandigkeit des sympathischen Ner- 

 vensystems von F. H. Bidder und A. W. Volk- 

 mann, Leipzig; 1842; p. 19. et seq. 



f Observationes Mieroscopica-, &c. Berol, 1838. 

 C- 13. 



