LECT. XII. XIII. DIRECT AND INVERSE CURRENT. 237 



tion of the current may pass above or below the ligature, 

 and thus confuse the results. 



When we apply the two poles, one above, and the other 

 below the ligature, as the current is not interrupted, but 

 only weakened, it follows that the phenomena will be the 

 same as if there was no ligature, except that they will be 

 more feeble. 



Different Effects of the Direct and Inverse Current. I 

 have hitherto purposely refrained from noticing here, the 

 difference which exists in the loss of excitability produced 

 by the passage of the electric current in the nerve, according 

 to its direction. When we transmit the current in a frog 

 prepared in the manner I have described, and placed 

 across two small glasses, we at first obtain contractions in 

 the limbs both at the commencement and at the termina- 

 tion of the passage of the current, whatever be its direction. 

 The second period of excitability, already described, soon 

 follows, and in this there is contraction in the limb traversed 

 by the inverse current, only at its cessation, and in that 

 traversed by the direct current only at its commencement. 



Let us now examine some phenomena which present 

 themselves, when we continue the passage of the current. 

 All contraction disappears, after a certain time, in the limb 

 traversed by the direct current, and we see contractions 

 continue in that limb only which is submitted to the action 

 of the inverse current, when the latter is interrupted. This 

 result, which may be obtained either on a living or a dead 

 frog, which may be also produced by causing the current to 

 act on the nerves only, evidently proves that the excitability 

 of a nerve is much more weakened by the passage of the 

 direct current, than by that of the inverse one. I shall 

 here show you some facts relating to this subject, which 

 appear to me clearly to prove that not only the inverse cur- 

 rent affects less the excitability of the nerve than the direct 



