136 ON NERVE-EXCITATION BY THE NERVE-CURRENT. 



inefficacy of currents having- their point of exit from muscle by 

 an artificial transverse section a fact which has also been pointed 

 out by Biedermann. 



I need hardly say that what has been advanced above stands 

 or falls with the theoretical assumptions upon which it rests. 



Concerning the liability of frogs kept in the cold to tetanic excitation . 



The frogs which I used for my experiments had been kept for 

 several months in a cellar,, at a temperature of about o. Since, 

 for each series of experiments, I used them immediately after they 

 had been fetched from the cellar, or, at any rate, after they had 

 been placed between a double window, at the temperature of o, 

 these frogs showed, with few exceptions, the disposition to enter 

 into tetanus which has already been remarked upon by Pfliiger 1 . 



This was especially the case with regard to Sana esculenta ; Rana 

 temporaria was much less inclined to fall into tetanus. What 

 I have to mention, therefore, relates in general to water-frogs ; 

 in experiments which were made on land-frogs, the fact is spe- 

 cially mentioned. 



If I divided the spinal cord of a R. esculenta which had been 

 kept in the cold (or, briefly expressed, a ' cooled frog '), tetanus 

 very rarely supervened in ttye inferior extremities ; but, on the 

 other hand, it did so almost constantly if the incision through the 

 spine was made so low as to affect the nerve -roots ; and the same 

 thing happened if I cut through the sciatic plexus. The strength 

 of the tetanus was very variable ; sometimes the limbs passed into 

 a prolonged and steady rigidity, which then gradually relaxed 

 through a stage of clonic spasms ; sometimes the spasms were clonic 

 from the first. Its duration was equally various, and occasionally 

 reached as much as four minutes. As a rule, the spasmodic stage 

 immediately followed the contractions caused by the incision, but 

 sometimes several seconds elapsed after the cessation of these 

 contractions as many as six before the preparation, which had 

 become quite quiescent after the incision, began to twitch again. 

 This was always a sign of a comparatively slight tendency towards 

 tetanus. 



I have made this remarkable tetanus after section of nerves 

 (which was not mentioned by Pfliiger, though it certainly must 

 have been known to him as to other observers) the subject of 



1 Untersuch. Uber die Physiol. des Elektrotonua, p. 133. 



