AFFERENT NERVES 233 



the ulnar side of the hand where the nerve is distributed. A 

 person whose limb has been amputated often seems to feels 

 pain in the extremity although it has been removed from the 

 body such pain coming from compression by the cicatrix 

 (or otherwise) of the nerves which before the amputation 

 were distributed to the severed limb. Htere, as in the case of 

 efferent nerves, division of the fibers between the seat of im- 

 pression and the center precludes the possibility of any ner- 

 vous manifestation. That is to say, no pain will be felt, no 

 matter how great the injury be, if the sensory fibers running 

 from the seat of injury be divided. Stimulation of the peri- 

 pheral end of a divided afferent fiber produces no effect; 

 but stimulation of the central end is followed by the ordi- 

 nary manifestation by pain if the nerve stimulated be a 

 common sensory one. This remark, of course, applies only 

 to those nerves which can be thus directly stimulated 

 typically to true sensory fibers. 



Impressions conveyed by nerves of special sense must be 

 received through the intervention of certain complex or- 

 gans, consideration of which belongs elsewhere. 



Although a division has been made of nerve fibers into 

 afferent and efferent, each with definite, proper and dissim- 

 ilar functions so far as the direction of conduction is con- 

 cerned, it has been impossible to discover any actual differ- 

 ence in the composition, appearance, or other properties, of 

 the actual fibers themselves. In fact, it may be even consid- 

 ered as only an accident that one fiber conveys a message 

 peripherially and another centrally an accident dependent 

 upon the kind of center with which the fiber is connected 

 and the kind of termination it has in the periphery. 



Direction of the Current in Nerve Fibers. It has long 

 been understood that in no case will a fiber in situ convey 

 a message at one time in one direction and at another in an 

 opposite one, that no individual fiber can be both afferent 

 and efferent; and so far as practical action is concerned 

 this is true, but "experiment has shown that if a nerve 



