NERVE-EXCITATION BY THE NERVE-CURRENT. 141 



by its own current, I have already mentioned that if the transversely 

 cut ends of two Sartorius muscles are allowed to fall one upon the 

 other with sufficient rapidity, and in such a way that the trans- 

 verse sections are in the same plane, so constituting a single 

 transverse section of both muscles, no contraction ever follows, 

 whereas there may be a strong contraction of both muscles if one 

 end of muscle falls upon the other so that the one is a prolongation 

 of the other, but with the two ends overlapping. Now in the 

 first case the two muscle-currents are opposed, and compensate 

 each other ; in the second, they have the same direction in the 

 circuit, formed by the two ends of the muscles. Making use of 

 this artifice, Kiihne 1 has in fact obtained contractions with the 

 nerve-current as well. I have likewise arranged the experiment 

 on this plan, and found that it succeeds with certainty on sufficiently 

 excitable frogs, provided only care be taken that the two ends of 

 nerve have not too much fluid adhering to them. As soon as they 

 were let fall one upon the other, the two legs contracted vigorously, 

 and sometimes even passed into a prolonged clonic excitation. 

 But if I dropped one nerve on the other so that the two trans- 

 verse sections were in one plane, neither contraction nor tetanus 

 occurred. 



If the sciatic plexus of a cooled frog has been divided close to the 

 vertebrae, or the nerves ligatured at that point, and then cut through 

 above it, and if the cut bundle of nerves is raised, firstly by means 

 of a fine glass rod, secondly by means of the thread, during the tetanus 

 or clonus of the leg consequent on section of the nerves, it is fre- 

 quently observed that the intensity of the tetanus or the form of 

 the clonus is at once altered ; if then the nerve is put back into its 

 moist and conducting bed, the original type of contraction forthwith 

 returns. One may repeat this with success, several times. If the 

 contractions of the leg are allowed to come to an end while the 

 plexus is kept raised, and if the plexus is then replaced upon the 

 ileo-coccygeal muscle, the contractions frequently reappear, although 

 generally to a much less degree. This only occurs provided the 

 ileo-coccygeal muscle has not been injured in the course of prepara- 

 tion. The cause of these phenomena (when muscle-currents do not 

 play a part in them) is to be found simply in this, that when the 

 plexus lies on the posterior wall of the pelvis, i^he nerve-current 

 is closed externally to the nerve, whereas this is not the case when 

 the plexus is raised. 



1 Loc. dt. p. 92. 



