ON NERVE-EXCITATION BY THE NERVE-CURRENT. 137 



special investigation, but I shall here mention only such points as 

 bear on what follows. 



To these belongs, in the first place, the fact that a second section, 

 when the muscles have become quiescent, generally causes a 

 renewal of the spasms, though they are as a rule weaker after 

 each new section. 



In the second place, it is to be remarked that the spasms are 

 usually stronger and more lasting the higher the nerve has been 

 cut. If I cut through simultaneously the sciatic plexus of one side, 

 and on the other the sciatic nerve in the thigh or just above the 

 knee, and then compared the spasms on both sides, after fixing the 

 knee so as to prevent any movements caused by the muscles of the 

 thigh, I found that the spasms were as a rule much weaker and 

 shorter in the last named limb, and that occasionally they were quite 

 absent even when the other side entered into active movements. 

 But if only a few such experiments are made it may perhaps be 

 found that this rule does hold good, for it is liable to many excep- 

 tions, the causes of which can only occasionally be assigned. Thus, for 

 example, the neighbourhood of injured and therefore electromotive 

 muscles may cause modifications. But in the large number of 

 experiments I made, the rule in question came out quite clearly. 



Preparations which gave strong tetanus by section of the nerves, 

 often reacted with a tetanus previously to such section, to closure 

 or opening, even when the battery-currents were only just strong 

 enough to act. Simple twitches were less frequent, and appeared 

 for the most part when the battery-current was closed several times 

 in succession in the same direction ; the first closure, for instance, 

 giving closure tetanus ; the second, clonic disturbance ; the third, a 

 simple twitch only. B/eversal of the current then restored tetanus. 

 All this appeared in a still more striking manner if I cut the 

 nerve, and applied the electrodes to the transverse and longitudinal 

 sections. With descending currents, even the weakest, I then 

 obtained a strong closure tetanus, and with ascending currents an 

 equally strong opening tetanus. And preparations which did not 

 respond by a tetanus to the section of their nerves, fell into a 

 strong closure tetanus (provided they were taken from cooled 

 frogs) as soon as I made a descending current, or broke an ascend- 

 ing current, having thus in the first case its point of entrance, in 

 the second its point of exit, at the transverse section. In these 

 experiments the unpolarisable electrodes were only from 2 to 3 mm. 

 apart. 



