SYMPATHETIC NERVE. cbd 



altogether of the grey kind, consisting of gelatinous fibres, with, as usual, a very few- 

 white or tubular fibres mixed with them ; and this observation has since been con- 

 firmed by Beck. The other cord either is entirely white, or more commonly, as 

 appears to me, is made up of a white and grey portion running alongside each other. 

 It seems highly probable that the white cords and the white fasciculi of the mixed 

 cords contain the cerebro-spinal fibres which the spinal nerves contribute to the sympa- 

 thetic, and that the grey cords and fasciculi are contributions from the sympathetic to 

 the spinal nerves. In corroboration of this view, Mr. Beck observes that the grey 

 cords on leaving the ganglia give small branches to the neighbouring vessels, and are 

 reduced in size before joining the spinal nerves. Another interesting fact respecting 

 these communications has been pointed out by the last-named observer somewhat 

 similar to that previously noticed in the frog, namely, that whilst the grey and white 

 connecting cords are in the thorax of nearly equal size, the grey one relatively increases 

 lower down, and in the pelvis constitutes the sole communication between the sacral 

 ganglia of the sympathetic and the spinal nerves, the white branches from the latter, 

 to the sympathetic passing over the sacral ganglia without joining them, to enter the 

 sympathetic plexuses sent to the pelvic viscera. 



The tubular fibres of each white communicating fasciculus can be traced back to 

 both the anterior and the posterior root of the spinal nerve, and pale fibres from the 

 grey fasciculus may be traced up into the anterior root, and as far as the ganglion of 

 the posterior root, which root has also pale fibres above the ganglion. Whether these 

 central pale fibres proceed from the sympathetic to the spinal cord (possibly to be dis- 

 tributed to its vessels), or are sent from the cord and spinal ganglia to the sympathetic, 

 or pass both ways, is as yet uncertain. 



As to the further progress of the cerebro-spinal fibres conveyed to the sympathetic 

 by the communicating branches, Valentin has endeavoured to show that, after joining 

 the main gangliated cord or trunk of the sympathetic, they all take a downward 

 direction, and after running through two or more of the ganglia, pass off in the branches 

 of distribution, leaving the trunk considerably lower down than the point where they 

 joined it. He conceives that this arrangement, which he calls " lex progresses," is 

 proved by experiments on animals, in which he found, that on irritating different 

 parts of the cerebro-spinal axis, as well as different branches of nerves, the visceral 

 movements which followed bore a relation to the point irritated, which corresponded 

 with the notion of such an arrangement. Volkmann and Bidder, on the other hand, 

 show that this opinion cannot be reconciled with the observed anatomical disposition 

 of the fibres, for there are fasciculi from the communicating branches which obviously 

 pass upwards ; nor will the experimental evidence in its favour apply to the upper 

 part of the sympathetic, where, as Valentin himself admits, motorial fibres must be 

 supposed to run in an upward direction to account for the contraction of the pupil 

 which follows section of the cervical part of the sympathetic. 



From what has been stated, it seems reasonable to conclude that nerve- 

 fibres take their rise in the ganglia both of the cerebro-spinal and sympa- 

 thetic nerves, and are in both kinds of nerves mixed with fibres of cerebral 

 or spinal origin ; that the ganglia are nervous centres which may probably 

 receive through afferent fibres impressions of which we are unconscious and 

 reflect these impression al stimuli upon efferent or motor fibres : that per- 

 haps, even, certain motorial stimuli emanate from them, the movements ex- 

 cited by or through the ganglia being always involuntary, and affecting 

 chiefly the muscular parts of the viscera, the sanguiferous, and perhaps the 

 absorbent vessels ; and that, in fine, the chief purpose served in the animal 

 economy by the ganglia and the ganglionic nerve-fibres, whether existing in 

 acknowledged branches of the sympathetic, or contained in other nerves, is 

 to govern the involuntary, and, for the most part, imperceptible movements 

 of nutrition, in so far at least as these movements are not dependent on the 

 brain and spinal cord ; for it must not be forgotten that there is unques- 

 tionable evidence to prove that the visceral and vascular motions are influ- 

 enced by nerve-fibres connected with the csrebro-spinal centre. 



