Physiology by the Laboratory Method; For Secondary Schools

Physiology by the Laboratory Method; For Secondary Schools

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1902 edition. Excerpt: ...We cannot give in an elementary treating of this wonderful and complex phenomenon a complete description of why and how the blood flows, nor consider the various conditions which modify its quantity and force. There are, however, general principles with which we should become acquainted: ----1. That the great propelling force of the circulation is the ventricular contraction of the heart. This force alone is sufficient to force the blood from the aorta through arteries, capillaries, and veins to the right auriele, or from the pulmonary artery to the left auriele. 2. That the other forces, as resistance offered by the size of the capillaries, the muscular coats of the arteries, and the veins, the elasticity of the arteries, the pressure due to the contraction of skeletal muscles, in connection with the valves of the veins, which prevent a backward flow, the influence of respiration, and the force of gravity, are not causes of circulation, but only forces which modify the eifect of the propelling force of the ventricular contraction. The great engine which forces the blood in its ceaseless round through artery, capillary, and vein is the heart. ' The rate and the quantity of the flow will depend-upon the rapidity and energy of the heart beat and the peripheral resistance. The heart' s contraction is due to the metabolic changes taking place in the heart muscle, and the heart contains within itself the stimulus for its contraction. In the embryonic heart there are no ganglia, and yet the heart beats rhythmically; the heart's beat is therefore independent of the influence from its ganglia. The force and frequency of the heart beat is under the influence of the central nervous system. The stimulus from the two vagi tends to...show more

Product details

  • Paperback | 176 pages
  • 189 x 246 x 10mm | 327g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236968158
  • 9781236968159