SYMPATHETIC NERVE. 



435 



characteristic specimens of either are examined 

 the difference is sufficiently marked ; yet in 



Fig. 285. 



From a branch of the coccygeal nerve inside the dura 

 mater of Man. (Mag. 350 diamC) After KoUiker. 



some parts of the branches of the sympathetic 

 in the higher animals it is difficult to limit the 

 two species of tissue, and between the most 

 characteristic of the fibres and many em- 

 bryonic tissues the most marked resemblance 

 exists. In the ultimate distribution of the 

 sympathetic there seem to be, as Kolliker 

 observes, none but fine tubular fibres present. 

 If, then, the fibres of Remak be kept out of 

 consideration, as not being possessed of the 

 properties of nerve-fibres, are there any fibres 

 in the sympathetic which can be regarded as 

 differing in their anatomical constitution from 

 those occurring in the nerves belonging to the 

 cerebro-spinal system? In 1812 Bidder and 

 Volkmann described particularly the distinc- 

 tion in point of structure between the tubular 

 fibres, which have been mentioned as being 

 present in the sympathetic. They measured 

 the tubular fibres, and found that while some 

 of them had a diameter of O'OOOiG to 0'00068 

 of an inch, others measured only 0-00012 to 

 0'00022; and between the two sizes they 

 observed no fibres of intermediate breadth. 

 They also measured the branches which enter 

 and those which leave the ganglia in the frog. 

 The latter were found to exceed the former in 

 point of thickness, which could only be at- 

 tributed to the addition of structures arising 

 in the ganglia, and on examination they ob- 

 served that the increase in thickness of the 

 one over the other was due to the presence 

 of a greater number of tubular nerve-fibres 

 belonging to the finer variety ; and hence it 

 was concluded that these are the peculiar 

 organic or sympathetic fibre. The coarser 

 variety they regarded as arising in the cerebro- 

 spinal centres, while the fibres belonging to 

 the finer variety always, according to them, 

 take their origin in the ganglionic system. 

 They describe these fibres as being about half 

 the diameter of those belonging to the cerebro- 

 spinal nerves ; they are further distinguished 

 by their paleness ; the absence, under all cir- 

 cumstances, of the double contour, and the 

 small quantity of curcllike contents which 

 they present even when examined some time 

 after death, and by their yellowish-gray colour 

 when in bundles. The distinctions between 

 the broad and fine tubular fibres, as given by 



Volkmann and Bidder, were denied by Valen- 

 tin, who stated that the fibres of these au- 

 thors were merely fibres of Remak. Reichert, 

 on the other hand, confirmed the observations 

 of Bidder and Volkmann as to the difference 

 in point of size and structure between the 

 cerebro-spinal nerve-fibres and the sympathetic 

 or organic fibres. The description which is 

 given by Remak of the gelatinous fibre does 

 not, as Volkmann and Bidder maintain, apply 

 to the fibres which they have described : they 

 are much finer, ten times finer, than the 

 cerebro-spinal fibres, whereas the fibres of 

 Bidder and Volkmann are generally only a half 

 narrower than these fibres. The relations of 

 the two structures towards reagents as well 

 as their general characters are also very dif- 

 ferent. 



Kolliker agrees with Bidder and Volkmann 

 that there are nerve fibres in the sympathetic 

 which are not derived from the cerebro-spinal 

 system, but arise from the ganglionic cor- 

 puscles; he farther confirms the observation 

 of these authors, that all the fibres which 

 arise in the sympathetic belong to the finer 

 variety of tubular fibres, and that they present 

 the characters which they were described by 

 Bidder and Volkmann as possessing ; he de- 

 nies, however, that they are peculiar to the 

 sympathetic system. Fine fibres agreeing with 

 these in structure arise, according to him, in 

 the cerebro-spinal system, as well as in the 

 sympathetic. Again, the diameter of the 

 coarser and finer varieties of the tubular nerve 

 fibres is by no means so strictly limited as 

 Bidder and Volkmann believed, there being 

 transitions from the finer to the broader or 

 coarser variety. Besides occurring in the sym- 

 pathetic, they are likewise present in the 

 anterior and posterior roots of the spinal 

 nerves, especially in the latter; and in the 

 brain and spinal* cord they exist in large num- 

 bers. Another objection to the views of 

 Bidder and Volkmann as to the peculiar na- 

 ture of these fibres is derived from the fact 

 that it is by no means uncommon for the 

 broader tubular fibres to divide into finer 

 fibres during their course to the periphery, 

 becoming narrower and narrower, and at the 

 same time losing their distinct double contour; 

 and hence in their ultimate distribution they 

 consist almost entirely of fine fibres, which 

 cannot be distinguished from those described 

 by Bidder and Volkmann as constituting the 

 peculiar fibres of the sympathetic system. 

 Volkmann himself now admits that the dis- 

 tinction between the broad or animal nerve- 

 fibre and the fine or organic is by no means 

 always strictly defined, and also that the 

 broad tubular or animal fibres, in their peri- 

 pherical distribution, assume the characters 

 of the others. It would appear, then, as Kol- 

 liker maintains, that there is no absolute dis- 

 tinction between the fibres of the sympathetic 

 and those belonging to the cerebro-spinal 

 system ; the difference is merely one of rela- 

 tion and degree : while the nerves of the latter 

 system consist chiefly of broad tubular fibres, 

 the sympathetic is chiefly composed of fine ones. 



F F 2 



