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Untitled Article
word * , necessarily omitting the references made to the diagrams , models , and real objects by which his lectures hare been so amply illustrated . * In man the heart is double—there are , in fact , two hearts , quite distinct in their action , and separated from each other by a strong partition , but closely united for the sake of convenience ; one for the
circulation through the lungs , the other for the circulation through the body in general . The first is called the Pulmonic , or the lesser circulation ; the second is called the Systemic , or the greater circulation . The apparatus for the pulmonic or lesser circulation consists , as in all the preceding examples , of veins , of an auricle , of a ventricle , and of an artery . The apparatus for the systemic or greater circulation , consists of precisely the same parts , of veins , an auricle , a
ventricle , and an artery . From the position of the heart when in its natural situation , the pulmonic heart is on the right side ; it is therefore called the right heart : while the systemic heart is on the left side ; it is therefore called the left heart . In the right heart there are two veins ; the one ahove brings the blood from the head , and the superior extremities ; it is called the superior vena cava ; ^ the one below brings the blood from all the lower parts of the body ; it is
named the inferior vena cava . The two ven < B cavie meet at one point , and pour their blood into the right auricle . The right auricle opens into the right ventricle . From the right ventricle springs a large artery , which is the pulmonary artery , and which divides into two large branches ; one of which goes to the right lung , and the other to the left . This completes the apparatus of the right heart . The capillary branches of the pulmonary artery , after ramifying through
the lungs , terminate in the capillary branches of the pulmonary veins ; the capillary branches of these reins uniting together , and becoming larger and larger , at length form four trunks , two for each lung . These are called the four pulmonary veins . These pulmonary veins convey the blood from the lungs to the left heart ; they open into the left auricle ; the left auricle transmits the blood to the left ventricle , the left ventricle to the great systemic artery , or the aorta , while the aorta carries it out to the system . '
The broad part or basis of the heart is placed upwards , its apex downwards . The heart itself is held in its position by a membranous bag which encloses it , and which is termed the pericardium . That the blood circulates in the course just described is proved by convincing arguments , by the valves , by the effect of ligatures , by injections into the vessel *; and , lastly , by the evidence of our senses , for it
may be observed in a living animal . The membrane of a frog ' s foot is sufficiently transparent to allow the circulation of the blood to be distinctly seen by the aid of a microscope , and without injury to the animal . It has been exhibited by Dr . Smith ; and those who have Watched the living currents rushing in continued streams along their appropriate channels , will not easily lose the impression which such an instance of the wonderful and the beautiful in creation is calculated to
convey , Thfc discovery of the circulation was made , as is well known , by HarVty , about tnG year 1620 . He spent eight years In rfe-examining the prdoft of the fact before making it known to the public , which h ^ did through the medium of a brief tract .
Untitled Article
196 Dr . Southwood Smith on the Animal Economy .
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Citation
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Monthly Repository (1806-1838) and Unitarian Chronicle (1832-1833), Feb. 2, 1833, page 126, in the Nineteenth-Century Serials Edition (2008; 2018) ncse.ac.uk/periodicals/mruc/issues/vm2-ncseproduct2608/page/58/
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