INFLUENCE OF THE NERVOUS SYSTEM. 177 



paralyzed member is, on account of the dilatation of its 

 vessels, warmer than the sound member; but continued 

 motion, and consequently, greater intensity of combustion, 

 in the latter, may cause a difference of temperature in the 

 opposite direction; and in this manner must be explained 

 those contradictory results of observations which have sug- 

 gested to V. Bezold the idea that the vaso-inotor nerves 

 of the inferior extremities remain on the same side of the 

 spinal cord, while those of the anterior extremity are inter- 

 laced along the medullary cord ; while Schiff has formed the 

 still, more singular hypothesis that the course of the vaso- 

 motors of the leg, the foot, the hand, and the forearm, is 

 direct ; whilst those of the pelvis, the thigh, the arm, and the 

 shoulder, are crossed. 



The vaso-motors spring from the cord by the anterior roots 

 of the spinal nerves. This fact has been put almost beyond 

 the reach of doubt by Claude Bernard's investigations of the 

 vaso-motors of the thoracic portion of those which control 

 the secretion of the saliva, and finally, of those sympathetic 

 branches which, without being exactly vaso-motors, bear the 

 closest relationship to these nerves. We mean those fila- 

 ments which control the oculo-pupillary phenomena, which 

 are observed to take place after section of the cervical sym- 

 pathetic cord (contraction of the pupil, sinking of the eye- 

 ball, etc.). 



What is remarkable, though, is that the height of the roots 

 from which the vaso-motors spring does not at all correspond 

 to the height of the organs or of those parts in which these 

 nerves are distributed : thus Cl. Bernard has demonstrated 

 that the vaso-motors which join the brachial plexus, and 

 then proceed to the thoracic portion, come to it by the 

 ascending filaments of the thoracic cord of the great sympa- 

 thetic nerve, those which join the sciatic nerve coming by 

 the descending filaments of the lumbar region cord ; they 

 thus emerge from the spinal cord : the former from much 

 lower, and the latter from much higher, roots than those of 

 the corresponding nerves to which they are afterwards united. 

 The oculo-pupillary sympathetic branches, finally, spring 

 from the spinal cord, by the roots of the first two dorsal 

 pairs, in a manner quite independent of the corresponding 

 vaso-motors. We see thus, that the study of the passage of 

 these nerves offers unexpected complications, and difficulties 

 which it is not easy to remove by experiment, their course, 



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