. A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction ... Physiology, Comparative. THE CIRCULATION OP THE BLOOD. 275. â "V.*^ The effect of vagus stimulation on the blood-pressure is always very marked, as would be supposed. To examine an extreme case, suppose the heart arrested for a few seconds, the elastic recoil of the arteries continues to maintain for a time the blood-pressure, though there is, of course, an immediate and pronounced fall. And it may bfe remarked, by-the-way, that in cases of fainting, when the heart ce
. A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction ... Physiology, Comparative. THE CIRCULATION OP THE BLOOD. 275. â "V.*^ The effect of vagus stimulation on the blood-pressure is always very marked, as would be supposed. To examine an extreme case, suppose the heart arrested for a few seconds, the elastic recoil of the arteries continues to maintain for a time the blood-pressure, though there is, of course, an immediate and pronounced fall. And it may bfe remarked, by-the-way, that in cases of fainting, when the heart ceases to beat, or beats in the feeblest man- ner, the importance of this arterial elas- ticity as a force, maintaining the circulation for sev- eral seconds at least, is of great importance. As seen in the tracing, the beats, when the heart commences its ac- tion again, tell on the comparatively slack walls of the arteries, distending them greatly, and this may be made evident by the sphygmograph as well as the manometer; indeed, may be evident to the finger, the pulse resembling in some features that following excessive loss of blood. If the heart has been â merely slowed, or its pulsation weak- ened, the effects will of course be less marked. The Quantity of Blood.âThe blood-pressure may also be augmented, the cardiac frequency remaining the same, by the quantity of blood ejected from the ventricles, which again depends on the quantity entering them, a factor determined by the condition of the vessels, and to this we shall presently turn. In consequence of changes in different parts of the system by way of compensation, results follow in an animal which might not have been anticipated. Thus, bleeding, unless to a dangerous extreme, does not lower the blood-pressure except temporarily. It is estimated that the body can adapt itself to a loss of as much as 3 per cent of the body-weight. The adaptation is probably not through absorption chiefly. , ng t. diac inhibition on bloo
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