Arhythmia of the heart : a physiological and clinical study . ledby Marey the compensatorypause. The explanation ofthis long pause Avas givenbyEngelmann,who showedthat in consequence ofthe extra-systole, the ven-tricle is still in the re-fractory phase when thenext physiological stimu-lus reaches it; this stimu-lus, therefore, has no effect,no contraction takes place,and it is not till the nextstimulus after it that acontraction can again beproduced. Thus the nor-mal systole that wouldfollow the extra-systole ismissed; then the first systole that comes after the compensatory pause ( post-compe
Arhythmia of the heart : a physiological and clinical study . ledby Marey the compensatorypause. The explanation ofthis long pause Avas givenbyEngelmann,who showedthat in consequence ofthe extra-systole, the ven-tricle is still in the re-fractory phase when thenext physiological stimu-lus reaches it; this stimu-lus, therefore, has no effect,no contraction takes place,and it is not till the nextstimulus after it that acontraction can again beproduced. Thus the nor-mal systole that wouldfollow the extra-systole ismissed; then the first systole that comes after the compensatory pause ( post-compen-satory systole) occurs exactly at the moment at which it wouldhave occurred had no extra-systole preceded it. In the diagramsB-E the compensatory pause is also shown. It is clear that thesooner the extra-systole interrupted the diastole, the longer is thepause. Thus the extra-systole bars the occurrence of the next followingphysiological systole, but in reality does not disturb the rhythm ofthe heart. Even after several successive extra-systoles which bar. Fig. I 10 ARHYTHMIA OF THE HEART two or more physiological beats, the first spontaneous systolealways reappears exactly at the moment at which it would haveoccurred if there had been no stimulation of the heart (F). Theoriginal rhythmical movement of the heart is invariably restored,a fact from which Engelmann formulated the law of the conservationof the rhythm of physiolofjical stimuli. If the heart or a portion of its wall is not left free to reply tospontaneous stimulation, but is thrown into rhythmical contractionby being tetanised, then an extra-systole produced by a strongartificial stimulus is not followed by a compensatory pause, for assoon as the refractory phase is over, and the contractility of theheart is sufficiently restored, the continuous stimulation producesanother contraction. This also affords a proof that the normalphysiological stimulus for the auricle and ventricle is not a con-tinuous, but a rhythmica
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