510 APPENDIX 



Expt. 77. Neuraxones Conduct in Both Directions. (Apparatus: 

 Cell, inductorium, key, sartorius.) Isolate the sartorius muscle carefully 

 and place it on the dried dissecting-plate. The motor neuraxones in this 

 muscle divide, one part going to each side of the lower end. Slit up the 

 middle line one-third of the broad end of the muscle, and stimulate with 

 the smallest strength of break induction-shock that will cause a contrac- 

 tion on one "leg" of the divided muscle, both electrodes being at the end 

 of the other.leg. Observe that with this stimulus, or one slightly stronger, 

 contraction takes place in the other leg of the muscle also. The efferent 

 neuraxones have conducted impulses afferently as well as efferently. 



Another place besides the sartorius muscle that this principle may be 

 demonstrated is on the nerves supplying the electrical organ of the electric 

 catfish (Malapterurus), where a single neuraxone supplies a large organ 

 that may be detached from the fish completely, and its nerve studied. 



Expt. 78. Effect Depends on Connections. (Apparatus : Inductorium, 

 key, frog-board.) Pith the brain only of a frog and place the animal 

 belly down on the frog-board. Cut out and away the upper third of the 

 spinal column (which extends from the head only to the urostyle). With 

 fine and small scissors cut away the bone at either side of the remainder 

 of the spinal cord (being very careful not to injure in any way the latter), 

 thus having the cord free of its vertebral bony covering. Observe the 

 posterior (afferent) roots and the large anterior (efferent or motor) roots 

 lying beneath them. 



(A) Afferent Fibers not Motor. Tie a ligature about the largest posterior 

 root close to the cord and cut the root between these. Stimulate with 

 very weak single induction-shocks the peripheral portion of the divided 

 root. Practically no leg movements occur. The posterior roots are 

 afferent. 



(B) Afferent Fibers Connect with Motor Neurones. Tie a ligature about 

 another of the large posterior roots as far as possible from the cord, 

 cutting the root peripherally to the ligature. Gently stimulate the central 

 portion. Muscular contractions occur. 



(O) Anterior Roots not Afferent. Cut through all the posterior roots of 

 the side on which Expt. B was performed. Stimulate mechanically and 

 chemically the skin of the leg on the same side. No movements occur. 

 Stimulate similarly the other leg. Movements occur in both legs. 



(D) Efferent Fibers Motor. Ligate a large anterior root close to the 

 cord and sever, as before, between the ligature and cord. Stimulate the 

 peripheral cut end. Contractions occur in the muscles attached. The 

 stimuli must be very weak. 



(E) Efferent Fibers do not Conduct Centrally to Motor Neurones. Tie 

 another anterior root far from cord, and cut peripherally to the ligature. 

 Stimulate as before near the central cut end. No movements follow. 



(F) Cut all the remaining anterior roots, and stimulate mechanically 

 and chemically the skin of the legs. Now no contractions whatever occur, 

 all the central connections being cut. 



No spinal root, however, is purely either afferent or efferent. 



