A treatise on anatomy and physiology / by W.P. Esrey.

  • Esrey, W. P. (William P.)
Date:
1851
Catalogue details

Licence: Public Domain Mark

Credit: A treatise on anatomy and physiology / by W.P. Esrey. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    when the heart is empty, and in fact after it has been removed from the body. The ventricles are the principal agents in the propulsion of the blood, for which purpose they have strong muscular parietes; the auricles have but slight contractile powers, their chief use being as receptacles. The contraction of the auricles and ventricles is not synchronous. The two auricles act together, as do also the two ventricles. The contraction of the auricles which forces the blood into the ventricles, is im- mediately followed by the contraction of the ventricles, during which the auriculo-ventricular valves are closed to prevent the regurgitation of the blood into the auricles, and consequently it passes into the aorta and pulmonary artery. Dilatation of all the cavities succeeds their contraction. The term systole has been given to the contraction of the heart, and that of diastole to its dilatation. The pulse is caused by the projection of the blood into the arteries from the ventricle, and corresponds with the contraction or systole. The contractile nature of the mus- cular coat of the arteries aids in the propulsion of the blood, and also in the production of the pulse. In the capillary and venous circulation there is no pulse. By the time the blood reaches the capillaries, the force of the heart is lost. Of the circulation carried on in this system of vessels but little more can be said than that it is due to vital action. The nutritive properties of the arterial blood are here yielded up, and the effete portions enter the veins to Le returned to the heart and lungs, there to be given off, or again vitalized. The forces which aid in returning the blood to the heart are: the suction power of the heart, muscular motion, and inspiration. When the heart dilates, and when the chest is expanded by the descent of the diaphragm, a vacuum is created, which the blood rushes towards the chest to fill. At every contraction of a muscle, the veins of the part are pressed upon, and their valves allowing the flow of the blood but in one direction, towards the heart, it must consequently be driven on in that direction. The muscular force of the heart has been variously estimated