in ELECTRICAL EXCITATION OF MUSCLE 181 



In conformity with this, "powerful intensities " of current are 

 required to produce contraction of the ureter by single in- 

 duction currents. Engelmann was the first to accomplish this by 

 taking metallic electrodes (zinc wires), shortening the intra- 

 polar tract, and connecting the primary coil of du Bois' induction 

 apparatus with 24 Grove cells. 



We have repeatedly stated that effects which can only be 

 determined in voluntary muscle by complicated methods and 

 the finest instruments, can be observed directly in smooth 

 muscle. This also applies in a marked degree to the 

 effect of duration of current upon excitation. It was shown 

 above that the marked difference in the height of maximum 

 twitches, according as excitation is with the induced or the 

 constant current, is a sign that duration of current is in the 

 last case an intrinsic factor. Fick was the first to establish exact 

 data re constant currents of uniform intensity and varying dura- 

 tion, for striated frog's muscle. This is much harder than in 

 smooth muscle, since, as might be presumed, the/ time during 

 which current must pass in order to produce a true excitation is 

 much shorter in striated muscle. And in fact in experiments 

 where closure has been effected by means of an ordinary key, 

 there is never any perceptible effect of duration of current on 

 the height (magnitude) of the twitch at closure, as may be 

 readily understood. If current once lasts long enough for the 

 muscle to reach its maximum of contraction, the closure twitch 

 cannot be affected by any further duration. And this must more 

 especially be the case when the circuit is opened and closed, 

 however quickly, by the hand of the operator. 



Under certain conditions striated skeletal muscle also becomes 

 modified, so that the relative inefficacy of very short stimuli is ex- 

 hibited, without any particular refinement of instruments. Briicke 

 found that the sensibility of striated muscle to short currents 

 diminished when it was curarised. It has long been known in 

 clinical medicine that paralysed striated muscles exhibit a certain 

 inability to react to short, induced currents, although their 

 relation to variations of the constant current is perfectly normal, 

 and this has been the basis of a great number of investigations 

 (6). Erb (I.e.), for instance, found in paralysis, such as Bell's 

 palsy in rheumatism, or by section of the nerve, that the 

 sensibility of the muscle to short currents was diminished, or 



