Doctrines of the Circulation C. 2

Doctrines of the Circulation C. 2

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1884 edition. Excerpt: ...follow each other in unceasing regularity. At the time of its motion three phenomena are noticeable: " First. That the heart is erected, and raises itself up into an apex; so that at that time it can strike the chest, and a pulsation may be felt externally. " Secondly. That it is contracted every way, but more so at the sides; so that it appears smaller, elongated, and drawn together. " Thirdly. If taken in the hand, it perceptibly hardens at the time of its motion: this hardening being due to tension, like that felt in the sinews of the forearm, which grow tense and more resisting when they move the fingers." In addition to the above, it can be seen in coldblooded animals, as fish and reptiles, that the heart " at the time of its motion grows paler; but when at rest is deeply tinged with the color of blood " (83). From these appearances Harvey draws the inference that the activity of the heart consists in a muscular tension and constriction of its fibres, producing induration and thickening of its walls and diminution of its cavities; and that, by this means and at this time, it expels the blood from its ventricles. This effect is especially indicated by the last-mentioned observation in cold-blooded animals, namely, that at the time of the heart's movement and erection it becomes pale from the absence of blood, while in its quiescence it resumes its deep red color. But this point is too important to be left for surmise; and Harvey's instinct carries him straight to the experimental test which shall settle it beyond dispute. " But no one," he says, " need have any further doubt about it; for if he make an opening into the cavity of the ventricle, he will see the blood escape forcibly at each successive tension or pulsation of the heart" (84)....
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Product details

  • Paperback | 78 pages
  • 189 x 246 x 4mm | 154g
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236667581
  • 9781236667588