ON NERVE-EXCITATION BY THE NERVE-CURRENT. 149 



equal to almost the entire length of a sciatic nerve, and the distance 

 of secondary from primary coil being as much as 40 cm. (i Dan. 

 6000 turns of sec. coil.) U was settled by this experiment that true 

 secondary action is possible from nerve to nerve. If I placed the two 

 nerves together, so that one was a prolongation of the other, with 

 their two ends however in contact for $ or 6 mm., all secondary 

 action was absent, as indeed was to be expected on theoretical 

 grounds. 



But still the above-described weak and exceptional results were 

 not sufficient to satisfy me. I saw that everything depended upon 

 the most intimate contact between the two ends of nerve, and that 

 if it were at all incomplete, or if the nerves had but a very little 

 lymph or salt solution adhering to them, the result was interfered 

 with. And so I came to think that it is very unpractical to take great 

 trouble in applying two nerves to each other, instead of using a 

 preparation in which the two bundles of nerve -fibres, which are to 

 serve as primary and secondary respectively, lie together naturally 

 in the same sheath. 



I decapitated a cooled frog, removed the upper extremities and 

 intestines, laid bare the sciatic nerve above the knee, ligatured with 

 the same thread its two branches, divided them below the ligature, 

 prepared the nerve up to near the point of origin of the branches to 

 the muscles of the thigh, divided the sciatic plexus, waited until the 

 consequent disturbance had subsided, and then, when all the muscles 

 were quiescent, excited the end of the nerve at the knee with weak 

 induction currents. The muscles, the nerves of which were still in 

 connection with the plexus, entered forthwith into strong secondary 

 tetanus, just as if I had excited these nerves directly. 



Often as I have since repeated this experiment it has never failed, 

 provided only that the preparation was sufficiently excitable to 

 give, in addition to the single contraction, a weak and fugitive mus- 

 cular disturbance in the thigh when the sciatic plexus was divided. 

 But I have also made the experiment with almost constantly success- 

 ful result, on cooled frogs land frogs in particular which did not 

 give the tetanic agitation after nerve section, if only I excited the 

 peripheral end of the sciatic very shortly after section. In those 

 cases, it is true, a strong secondary tetanus was not reached ; there 

 was for the most part only a tetanic or clonic agitation of the 

 muscles, just as may be seen with nerve-muscle preparations, the 

 nerves of which are excited with excessively weak, that is to say 

 barely efficacious, induction currents. 



