58 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 



tinuity between the two ends of the muscle. Beginning at one end of 

 the muscle, cut across the nerve terminals repeatedly, noting that the 

 fibers in the other end of the muscle then contract. Do not stimulate 

 with the electrodes, because this might invite the criticism that the con- 

 traction of the distant fibers is due to current skipping. The neigh- 

 boring gracilis muscle may also be used for this experiment. 



Annotation. This motor nerve conducts ordinarily in a centrifugal direction. 

 Since the stimulation of its terminals in one end of the divided muscle also gives 

 rise to a muscular response in the other end of the muscle, the impulses here gener- 

 ated must be conveyed in an afferent direction to the nearest divisions of these 

 efferent fibers, whence they proceed over the normally efferent fibers to the other 

 pole of the muscle. In this way a normally efferent fiber may be made to conduct in 

 an afferent direction. While it is probable that this nerve contains a certain number 

 of afferent neurons, their presence cannot nullify the significance of this experiment, 

 because in the event of their activation their impulses could only be transferred to 

 the other end of the muscle by changing their normally afferent into an efferent 

 type of conduction. 



