348 MOTION IN ANIMALS AND PLANTS. 



muscle can not be applied to a normal one. All that it is required to 

 prove is that it is possible for a spasm which is not discontinuous to 

 be as effectual for the doing of external work as a normal contraction. 

 It can hardly be disputed that the contraction of a veratrinized muscle 

 is continuous. It is, therefore, no longer possible to assert that dis- 

 continuity is essential to functional capacity. 



That our results differ from those of other observers is to be attrib- 

 uted to the mode of using the alkaloid and to the homeopathic minute- 

 ness of the dose. We estimate the quantity of veratrine which actually 

 enters the muscle not to exceed one ten-thousand of a milligram. 



THE HEART. 



We now turn from the skeletal muscles to the organ by the rhyth- 

 mical contractions of which the circulation is maintained. The mechan- 

 ical response of cardiac, like that of skeletal, muscle can be evoked 

 either directly or indirectly, but the heart has this peculiarity, that 

 each part of it has attributes which we are accustomed to regard as 

 nervous rather than muscular. It has, above all, the property which 

 belongs, as we have seen from our ex^^^eriments with strychnine, to the 

 motor cells of the spinal cord — that of dischai'ging itself rhythmically 

 when in a state of continuous excitation. It is characteristic of heart 

 muscle that it exhibits alternating periods of rest and activity, and we 

 have now the clearest evidence that it is not in virtue of its possessing 

 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 docs 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 

 instantaneous 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 electrometer for measuring the electromotive force of cur- 



