1 7 6 THE CONTRA CTION OF CARD I A C MUSCLE. 



standstill without provoking any more rhythm of excitation than an 

 occasional beat or two upon each separate turn of the screw, just as may 

 be seen when the ligature or the clamp is applied to any part between 

 the sinus and the ventricle. 



I conclude, then, that the phenomena following upon section are of the 

 same kind wherever that section is situated ; the part in connection with 

 the sinus continues its regular beat ; the part separated from it remains 

 still for a variable time, and then, according to its inherent rhythmical 

 power, develops a rhythmical beat of its own, the rate of that rhythm 

 when fully developed, and the length of time that the standstill lasts, 

 being correlated with the rhythmicity of the tissue. Further, the same 

 experiment can be applied to every part of the heart, for I have seen 

 the same kind of standstill, followed by a rhythm of development, take 

 place when a strip of muscle, taken from the apex of the ventricle or 

 the auricle, is suspended in the same way as the whole ventricle or 

 auricle. 1 It is true that the development of this spontaneous rhythm 

 is assisted by the occasional stimulation of the strip by means of a 

 weak tetanising current, and the regular testing of the condition of 

 the strip by means of single induction shocks ; but it is not true that 

 such rhythm is dependent upon such artificial stimuli, and owes its 

 existence to polarisation phenomena in the strip, as suggested by 

 Langendorff', 2 for, as pointed out in my paper, 3 I have seen control 

 strips develop a spontaneous rhythm, when they have simply been 

 suspended, and have not received a single electrical stimulus of any kind : 

 the only difference between the two strips being, that the one which had 

 been taught to beat commenced its spontaneous contractions quicker 

 than the control. 



In addition, as mentioned in the same paper, 4 the strip from the 

 ventricle, when once spontaneously beating, will continue to beat for as 

 long as thirty hours ; since then I have once observed a strip from the 

 apex of the ventricle, suspended in a moist chamber, beat for as long a 

 time as a hundred hours. Clearly, then, this rhythm cannot be explained 

 by any artificial electrical action. It is, I think, highly probable that 

 the tension of suspension plays a distinct part in its causation, just as the 

 tension of distension in the case of the apex of the frog's ventricle ; 

 though, that it is not entirely dependent on the stimulus of tension, is 

 seen by the fact that the strip or even parts of the strip will continue 

 beating rhythmically in a watch glass, after the spontaneous rhythmical 

 beat has once become well established. The main condition necessary 

 for the establishment of this rhythm is, it appears to me, some unknown 

 factor in the nutrition of the tortoise, for since the publication of that 

 paper I have attempted to demonstrate to my class the spontaneous beat 

 of the strip whenever I have managed to obtain a tortoise, and have been 

 much annoyed to find that again and again I have failed to obtain any 

 sign of rhythmical activity in the strip, and, even more than that, I 

 have sometimes failed to obtain any spontaneous activity in the isolated 

 entire ventricle. During the years 1882 and 1883, when my tortoise 

 experiments were in constant progress, I had a large supply of animals, 

 carefully tended, fat and healthy, in the very best condition, and I never 

 failed once in obtaining the results described in my paper. 



1 Op. cit., pp. 51-56. 



2 "Rhythmik und Automatik des Frosch-herzens," Leipzig, S. 57. 



3 Op. cit., p. 54. 4 Ibid., p. 53. 



