144 rilYSIoLOiiY OF MUSCLES AND NKUVKS. 



anode. If an a-cending current is passed through a 

 nerve, the anode side is situated in its lower portion j 



but it' lli' ciirrcnt is descending, then it i- situated in 

 the upper portion. If Hitter's tetanus is induced by 

 mean- <if a descending current, and if the nerve is bi- 

 sected between the electrodes immediately after the 

 opening of the current, the tetanus at once ceases. If 

 the same experiment 'is tried with an ascending current, 

 then the cutting of the nerve in no wav influences the 

 tetanus. 



Yet another proof of the truth of this hypothesis is 

 afforded by Prluger's study of the excitement of the 

 seiiMry nerves by an electric current. As the terminal 

 apparatus of sensory nerves, by the action of which the 

 irritation is recognised, is situated at the opposite cud 

 of the nerve, it seems that the law of pulsations should 

 prevail in an opposite way to that in which it pre- 

 vails in the ca-e of the motor nerves. Prliiger as- 

 certained that in reality strong ascending currents 

 induce sensation only when closed, strong descending 

 currents only when opened. The explanation is the 

 same in this case as in that of the motor nencs. On 

 the closing of the descending current, excitement oc- 

 curs in the lower portion of the nerve. In order to 

 effect -eii.-ation the excitement must pass to the spinal 

 marrow and the brain ; it would have, therefore, to pa-s 

 through the upper parts .if the nerve, \\here it would he 

 checked by the strong anelectrotonus which prevails 

 there. The opening ,,f the a-ceiiding current ha- a 

 similar irritating effect on the l\\er parts < if the nerve. 

 In order in reach the spinal mai row and brain, this 

 excitement \\.nild ha\eto pass through the upper parts. 

 \\here, in this ca-e, it \\oiil.l be checked by the strong 



t i\e modification* 



