

AFTER ELECTRICAL STIMULATION. 263 



While negative variation falls off only very slightly or not at all 

 with good nerves when moderate stimulations are frequently re- 

 peated, notwithstanding the shortness of the intervals between the 

 individual stimulations, positive after-variation, as far as I could 

 see, attained its maximum after the first stimulation, declining 

 with succeeding stimulations, at first very quickly, then more 

 slowly, and finally almost imperceptibly. In spite of very fre- 

 quently repeated moderate stimulations of short duration, I never 

 saw the positive variation quite disappear, although in comparison 

 with the negative variation which for a long period remained 

 unaltered, it was very small. In this statement it is assumed, 

 however, that the nerves which demonstrate this point are healthy. 



One example will suffice. 



Cold frog. Both nerves used at the same time. Du Bois induction-coil. Gal- 

 vanometer tract 7 mm. Intermediate tract 26 mm. Duration of stimulation 12 sees. 

 Alternately with and without switch. 



Current of electrodes + 40' Nerve current + 294. 



Positive after- variation increases up to a certain limit with in- 

 creased duration of stimulation. It was already noticeable when the 

 period of stimulation was only a fraction of a second, and after a 

 stimulation of a second's duration it was at times considerable. The 

 increase dependent on duration of stimulation is only conspicuous 

 when the duration is very short, subsequently it only increases very 

 slightly with increased duration; it falls again when duration of 

 stimulation exceeds a certain limit, and finally with further increase 

 quite disappears. With a stimulation which lasted for five minutes, 

 I found in two instances after cessation of stimulation not only 



