and Plants to the Electrical Phenomena associated with it. 61 



an intrinsic nervous system that it has this property. In another 

 important respect it resembles the motor apparatus of the cord, namely, 

 that its relations to stimuli are governed by what has been called the 

 " all or not at all " principle. It either does not respond or, if at all, 

 responds completely. In these respects, therefore, the action of the 

 heart is comparable neither with that of muscle acting independently, 

 nor even with that of the muscle nerve preparation, but rather with 

 that of muscle acting under the direction of the motor neuron which 

 governs it. 



I began the investigation of the electrical phenomena of the heart's 

 beat in 1881 with Mr. Page. We made out two new facts, namely, 

 that the electrical change which is evoked by excitation of the surface 

 is propagated, at a rate dependent on temperature, not in one direction 

 only but in all, as Engelmann had already shown to be the case with 

 regard to the wave of contraction ; and secondly, that the monophasic 

 variation is not, as had been supposed by previous observers, an instan- 

 taneous change, but lasts during the whole period of energetic systole. 

 But neither Mr. Page nor I understood then the nature of the initial 

 " spike," which is so striking a feature in the photographic record of 

 the variation in the uninjured heart. For its explanation I am indebted 

 to Mr. Burch, whose investigations on the use of the capillary electro- 

 meter for measuring the electromotive force of currents of short 

 duration have been of so much value to physiologists. The moment it 

 was understood that the spike indicated a diphasic variation analogous 

 to that of the muscle, I felt that I had the key to the complete under- 

 standing of my own previous observations. I was, moreover, able to 

 bring these into "omplete harmony with those of Professor Engelmann 

 made about the same time with the rheotome and galvanometer. 



Let me ask your attention to the photographic curves of the diphasic 

 and monophasic variations which I have placed one above the other in 

 synchronic relation to each other. It is to be noticed that the move- 

 ment of the recording surface is very slow, about a centimetre a second 

 only. To obtain the monophasic curve you have to place the distal 

 electrode on a spot which has been devitalised by scorching, and which 

 is consequently physiologically inactive, the proximal electrode on the 

 living surface near the junction between auricle and ventricle. The 

 instantaneous stimulation is applied to the auricle some couple of 

 millimetres distant from the proximal leading-off electrode. The Reiz- 

 welle is propagated from the auricle to the base of the ventricle and 

 then on to the devitalised spot, so that before it arrives at the contact 

 it is extinguished.* Consequently the change which is expressed by 

 the electrometer-curve takes place exclusively at the proximal contact- 

 surface. It differs only from the monophasic variation of skeletal 



* This mode of observation corresponds to the first fundamental experiment in 

 muscle (see. p. 45). 



