in ELECTRICAL EXCITATION OF MUSCLE 195 



(11) observed the non-gauglionated apex of the frog's heart 

 to pulsate rhythmically, when a constant electrical current 

 was led through it, this easily verified fact has been the 

 subject of repeated experiments. The frequency of pulsation 

 increases in a certain range with the strength of the current. 

 We have already seen that cardiac muscle responds _by_ 

 rhythmical manifestations of excitation to other continuous, 

 uninterrupted stimuli, e.g. mechanical and chemical, so that 

 the effect of sustained passage of current as just described is 

 nothing extraordinary, and the only question is whether this 

 property really is specific to cardiac muscle, and is not rather 

 a general characteristic, as it were abnormally developed. 

 Hering (13) long ago observed that a curarised frog's sartorius 

 became rhythmically excited under certain conditions when its 

 intrinsic longitudinal current was short circuited by immersion in 

 0*6 / Q NaCl, and also when acted upon by very weak artificial 

 currents, the reaction being similar to that of chemical ex- 

 citation, according to Kuhne and Biedermann. This however 

 only referred to weak contractions in an unloaded muscle that 

 was moreover dipping into fluid. Later on we succeeded in 

 producing a long series of vigorous twitches, by means of uniform, 

 persistent closure of a battery current, in a loaded sartorius ex- 

 tended in Hering's double myograph, provided the excitability 

 of the muscle - substance was locally increased at the seat of 

 direct excitation (i.e., as will be shown, the kathodic end of the 

 muscle) by treatment with adequate solutions of Na.,C0 3 , from 

 1-3 % (14). 



Fig 82, a, shows such a series of curves, recorded after fifteen 

 minutes' continuous action of a 2 / Q solution of Na 2 C0 3 on 

 the tibial end of a curarised sartorius, during closure of a medium 

 descending current. A rapid shortening (twitch) of the muscle 

 begins before the first pronounced twitch has expired, long before 

 the descending shoulder of the curve has reached the abscissa. 

 The superposition of three twitches in rapid succession brings the 

 second contraction to the first maximum, after which follow in 

 regular rhythm twenty -five vigorous single twitches, hardly 

 inferior in size to the initial twitch ; these, at first closely packed 

 together, are discharged later at intervals of about one second. 

 After the twentieth twitch, the magnitude of shortening diminishes 

 rapidly, and at last only a trace of persistent contraction remains, 



