SYMPATHETIC NERVE. 



447 



examined, after addition of dilute solution of 

 soda, with a power of 40 diameters, it is not 

 difficult to observe, in the cat or other small 

 animals, that the fibres composing the white 

 portion run towards the centre. Many of 

 them bend directly inwards to the cord^ while 

 others sink into the spinal nerve, more or less 

 obliquely, still, however, in the direction of the 

 centre. That the fibres in question are not 

 to be regarded as fibres sent from the sym- 

 pathetic to the cerebro-spinal nerves is ren- 

 dered further probable by the fact that they 

 can all be traced beyond the corresponding 

 sympathetic ganglion into the cord above and 

 below. Moreover Kolliker has traced them 

 not only past the ganglia in the main chain 

 of the sympathetic, but into the peripherical 

 branches, and, in small animals, even through 



the ganglia occurring upon these latter He 

 also finds that the fine fibres in question differ 

 from those which arise in the sympathetic 

 ganglia in presenting a darker contour and 

 in being somewhat broader. 



As regards the proportion between the 

 fibres in the communicating branches which 

 may be regarded as proceeding from the sym- 

 pathetic to the cerebro-spinal nerves and those 

 which are sent by the latter to the sympa- 

 thetic, we have already seen that in the frog, 

 according to the observations of Bidder and 

 Volkmann, the former exceed the latter con- 

 siderably. In the higher animals it would 

 appear that the reverse is the case ; in the 

 rabbit, according to Kolliker, by far the 

 greater portion of the rami communicantes run 

 towards the centre. In man also, according 



Fig. 293. 



Connection between the sympathetic and the sixth intercostal nerve in the Rabbit. 



K c, communicatin g branch ; c P, intercostal nerve ; c, its central extremity ; p, its peripheral 

 extremity. Most of the fibres of the communicating branch run towards the centre ; several of 

 these, a, a, disappear among the fibres of the intercostal nerve, rather in the direction of the periphery. 

 (Mag. 60 diam.) 



to the same observer, much the greater number 

 of the fibres contained in these branches run 

 inwards towards the spinal column. I 

 examined most of the rami communicantes in 

 a foetal calf about 2 feet in length, and have 

 little hesitation in saying that in this animal 

 the proportion of fibres which are directed 

 towards the spinal cord greatly exceeds any 

 that appear to run towards the periphery. 

 At the point of junction with the spinal nerve 

 the communicating branch, when examined 

 with a power of 40 diameters, was seen to 

 spread out somewhat, most of the fibres bent 

 directly inwards towards the spinal cord, 

 others passed into the nerve, either obliquely 

 or at right angles to it, and then curved in- 

 wards towards the spinal cord. In some of 

 the communicating branches, a few of the 

 fibres were seen to join the nerve in the direc- 

 tion of the periphery. In the cat also, the fibres 

 of many of the communicating branches were 



found to run exclusively in the direction of 

 the spinal cord. 



The fibres in the different communicating 

 branches, as shown by Wlitzer, Miiller, and 

 others, are connected both with the anterior 

 and posterior roots of the spinal nerves, and 

 it seems probable that the fibres which are 

 sent from the cerebro-spinal system are de- 

 rived from both. Volkmann*, however, as 

 will be afterwards noticed, believes that all 

 the fibres sent to the sympathetic are derived 

 from the posterior root alone. 



As regards the further course of the fibres 

 which are derived by the sympathetic from 

 the cerebro-spinal system, Valentin f, holding 

 the view that this nerve is entirely composed 

 of such fibres, believed that on joining the 



* Nerven-Physiologie in Wagners Handworter- 

 buch, Eilfle Lieferung, p. 609. 



t De Functionibus Nervorum, 152. 155. See 

 also Quain's Anatomy, by Sharpey. 



