On some points in the innervation of the mammalian heart / by W.M. Bayliss and Ernest H. Starling.

  • William Bayliss
Date:
1892
Catalogue details

Licence: Public Domain Mark

Credit: On some points in the innervation of the mammalian heart / by W.M. Bayliss and Ernest H. Starling. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    4/14
    seems also to be a difference in the rapidity of propagation of the exci- tatory process in the two directions. The time that elapses after stimu- lation of the auricle before the ventricular lever rises is from T5 to T6. In the reversed direction the interval is longer, T9 to ’22. These numbers however are the result of only a few observations, since we are not certain that our methods of recording can give accurately enough the exact times at which the contractions of the auricles and ventricles begin. We hope to investigate the subject more fully, taking the first electrical change as the index of the arrival of the excitatory process. By photographing the electrical changes, with the help of a capillary electrometer, we hope to come to a certain conclusion on the subject. Action of Vagi. A. On Auricle. The action of the vagus on the auricle is fairly familiar from the work of Johansson and Tigerstedt1, McWilliam, Roy and Ad ami on the subject. As in the tortoise’s heart, it may act either on force or rate of contraction ; or, as in the majority of cases, both these effects may be combined. The effect on force however is by far the most marked. We have frequently obtained tracings in which the rhythm was unaltered, although the strength of the auricular con- tractions was markedly diminished. On the other hand, we have never obtained a tracing presenting an effect on rhythm alone, although this is often affected before the strength of contraction. Depression of the auricular beat under vagus excitation may occur to such an extent that it is exceedingly difficult to be certain whether the auricle is beating or not—the beats in fact seem to be reduced to invisibility. Thus we have often, under strong vagus stimulation, thought that the auricles had entirely ceased beating and that the ventricles were beating with their own proper rhythm. But on screwing the auricular lever away from the drum, so as to avoid the least possible friction, a tiny movement of the lever was so seen immediately preceding each ventricular beat, although the auricles themselves, as observed by the eye, seemed perfectly motion- less. In fact, we should say from the results of our experiments that it is extremely difficult, even using strong vagus stimulation, to cause complete cessation of auricular contraction. It seems possible that an excitatory process may occur in the auricle and may be transmitted thence to the ventricle, without causing any appreciable (i.e. registrable) contraction of the auricle itself. 1 Johansson and Tigerstedt. Hygieia Festband, 1880.