650 SYMPATHETIC AND OTHER SYSTEMS OF NERVES. 



but that a few run to it by the grey rami. There is not, however, any 

 definite physiological evidence for the existence of such afferent fibres. 



Loss of medulla by pre-ganglionic fibres. We have already seen 

 reason to believe that some of the pre-ganglionic fibres of the splanch- 

 nic nerve lose their medulla on their way to the pre-vertebral ganglia 

 (cf. p. 648). The evidence that pre-ganglionic fibres are not necessarily 

 medullated up to their terminations, is still stronger in the case of the 

 vertebral chain. 



By the degeneration and by the nicotin method, it can be shown 

 that in the cat fibres run from the upper lumbar white rami to the 

 sacral and coccygeal ganglia without passing through nerve cells. In 

 the rabbit the nicotin method only has been tried ; it gives the 

 same results. We may then conclude that in the rabbit there are pre- 

 ganglionic fibres, stretching from the upper lumbar white rami to the 

 sacral and coccygeal ganglia. But since the sympathetic in the sacral 

 and coccygeal region of the rabbit contains very few medullated fibres, 

 it follows that the pre-ganglionic fibres in this region must be non- 

 medullated, and as they are medullated in the white rami, they must 

 become non-medullated in passing down the sympathetic chain. In 

 other words, pre-ganglionic fibres may become non-medullated some 

 distance from their termination in the vertebral ganglia. 



Post-ganglionic medullated fibres. Although Eemak discovered 

 non-medullated nerve fibres (organic fibres) in 1838, 1 their nervous 

 nature was not generally accepted till about 1860. Thus, most of the 

 early observers who believed that the sympathetic ganglia gave off 

 nerve fibres at all, necessarily believed that they gave off medullated 

 nerve fibres (primitive nerve fibres, tubular fibres). Those observers, 

 on the other hand, who accepted the nervous nature of Remak's fibres, 

 were inclined to think that these alone were sympathetic fibres, and 

 that all medullated fibres were of cerebro-spinal origin. As time went 

 on, the observations of Bidder and Volkmann 2 on the origin of small 

 medullated fibres from sympathetic and spinal ganglia seemed more and 

 more irreconcilable with the results of research, and in consequence less 

 and less attention was paid to them. Thus, some writers passed by the 

 question of the medullation of ganglionic nerves, without even con- 

 sidering it, and others took for granted that no further proof was 

 required to show that all fibres given off by sympathetic nerve cells are 

 non-medullated. 



The proof brought forward by Bidder and Volkmann, that in the 

 frog small medullated fibres arise from sympathetic ganglia, was fairly 

 conclusive. The essential part of the proof was the fact that many 

 more small medullated fibres run from the sympathetic ganglia to the 

 periphery, than run to the ganglia from the central nervous system. 

 As at that time there was practically no knowledge of the connection 

 of nerve cells with nerve fibres, or of the finer structure of the ganglia, 

 it might have been objected that the increase in the number of fibres 

 peripherally of the ganglia was merely due to a division of nerve fibres 

 in them. But, in the light of our present knowledge of the ganglia, 

 Bidder and Volkmann's proof must be regarded as conclusive. They 

 showed also, and in the same way, that the ciliary ganglion gives off 

 medullated fibres. 



1 Remak, "Observ. anat. et micros, de systematis nervosi structura," Berlin, 1838. 

 2 "Die Selbststandigkeit des sympathise!) en Nervensystems," Leipzig, 1842. 



