Abstract
In a previous report 1 on the action of the vagus in bulbar anaemia induced by temporary occlusion of the head arteries, it was shown that, after division of both vagi, the heart rate does not change during the anaemic rise of blood-pressure, but remains at whatever maximum rate was attained after vagotomy.
It has been thought desirable to find out the effect on heart rate during the cardio-vascular response to bulbar anaemia, of removal of the stellate ganglia through which run the accelerator fibers to the heart. Accordingly, in a series of cats, after a control occlusion had been done according to the usual method, 2 the stellate ganglia were excised and further occlusions were done. Following is a typical result of such an experiment.
It is evident from the above table, that, with the accelerators eliminated, the vagi are over-active in holding the heart rate down. Under such conditions, recovery of the medulla after the circulation has been restored to the head arteries may, at times, be somewhat difficult, owing to the combination of low blood-pressure and slow heart rate. Moreover, this activity of the vagus is in evidence at a time when blood-pressure is at spinal level and all other signs of bulbar activity are in abeyance. In the experiment which has been given above, the vagi were sectioned in the recovery period, and heart rate increased immediately from 94, at which it had been for about five minutes, to 156; while blood-pressure rose from 40 to 70 millimeters of mercury.
With both vagi and stellates divided, the heart rate during the remaining occlusion period in the above experiment, remained between 156 and 162, which one would consider relatively constant. Whether the adrenals play any part in the maintenance of heart rate in the denervated heart under conditions of bulbar anaemia, is, at present, under investigation.
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