I/O 



PHYSIOLOGY OF NERVE. 



[CH. xv. 



/foot 



Spinal Nerve - 



Fig. 181. Diagram to illustrate recurrent 

 sensibility. 



France by Magendie (1822). These observers found that on 

 section of the anterior roots there resulted paralysis of the 

 muscles supplied by the nerves ; on section of the posterior 



roots there was loss of sensation. 

 These experiments clearly pointed 

 to the conclusion that the anterior 

 roots contain the efferent (motor) 

 fibres ; and the posterior roots the 

 afferent (sensory) fibres. This 

 conclusion was confirmed by the 

 experiment of stimulation. Stimu- 

 lation of the peripheral end of the 

 cut anterior root caused muscular 

 movement ; of the central end, no 

 effect. Stimulation of the central 

 end of the cut posterior root 

 caused pain and reflex move- 

 ments ; of the peripheral end, 

 no effect. 



Recurrent sensibility. 

 \ One of the statements just 

 made requii'es a slight modi- 

 fication ; namely, excitation 

 of the peripheral end of a 

 divided anterior root will 

 evoke pain and reflex move- 

 ments, as well as direct 

 movements ; that is to say, 

 the anterior root though 

 composed mainly of motor 

 fibres contains a few sensory 

 fibres com ing probably from 

 the membranesof the spinal 

 cord, and then running into 



Fig. 182. Diagram to illustrate Wallerian de- 

 generation of nerve-roots. the posterior root with the 



rest of the sensory fibres. 



They often, however, run down the mixed nerve a considerable 

 distance before returning to the posterior roots. 



The upper diagram on this page (fig. 181) illustrates the course 

 of one of these recurrent fibres (r) ; the arrows represent the 

 direction in which it conveys impulses. 



Degeneration of roots. The facts in connection with this 

 subject were made out by Waller (1850), and may be best 

 understood by referring to the next diagram (fig. 182). 



