THE NERVOUS SYSTEM. 481 



spinal ganglia, should be regarded as roots of the sympathetic. 

 But I think I have noticed in the Rabbit and in Man, that the 

 rami communicantes have chiefly a central destination. Still, 

 in man, fibres also occur very frequently — according to Luschka 

 always, — which must be regarded as branches of the sympa- 

 thetic going to the peripheral distribution of the spinal nerves, 

 from which again twigs are given off to nerves of the vertebrae ; 

 Avith respect to which conditions the more detailed observations 

 given in my ' Mikroskop. Anatom./ II, p. 525, and particularly 

 those of Luschka ('Nerven des Wirbelcanals/ p. 10 et seq.) may 

 be consulted. With regard to the question, whence the fibres 

 are derived which join the main trunk of the sympathetic from 

 the spinal nerves, it is certain that that portion of the rami 

 communicantes, which arises, from the motor root, and which, 

 according to Luschka, is always a white filament, takes its 

 origin from the cord (or brain) itself, but as regards the other, 

 proceeding from the sensitive root, it may be formed, in part or 

 wholly, from fibres originating in the ganglion. The latter, 

 however, appears to be improbable, for two reasons : 1. because 

 in that case, the existence of conscious sensations from parts 

 supplied by the sympathetic would scarcely be conceivable ; and 

 2. because the fibres originating in the spinal ganglia are of 

 medium size, whilst, in the rami communicantes, upon the whole, 

 only a few of that kind occur, and these, moreover, must be 

 referred to the motor root. 



We may here offer a few remarks upon the fine fibres of the 

 ganglionic nerves. It has been long known, that the sympa- 

 thetic contains a larger proportion of finer nerve-fibres than 

 the cerebro-spinal nerves, but it was not till 1842 that Bidder 

 and Volkmann laboured to show, that these fibres are not 

 only smaller, but also, in other respects, anatomically different ; 

 on which account, in contra-distinction to the thick fibres of the 

 cerebro-spinal nerves, they termed them sympathetic nerve-fibres. 

 In opposition to this, Valentin ('Rep./ 1843, p. 103) and I 

 (' Sympath./p.lO et seq.) have endeavoured to prove, that the fine 

 fibres in the sympathetic do not constitute a special class, and in 

 this I think we were tolerably successful. The principal reasons 

 are as follows: 1. Fine and thick nerve-fibres do not differ in- 

 trinsically in any essential respect except in size, and present the 

 most numerous intermediate dimensions. 2. Fine nerve-fibres 

 i. 31 



