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THE VASCULAR SYSTEMS 



blood, which is collected by the veins and through them returned to the right 

 auricle of the heart. From this cavity the deoxygenated blood passes into the 

 right ventricle, from which it is conveyed through the pulmonary arteries to the 

 lungs. In the capillaries of the lungs it again becomes arterialized, and is then 

 carried to the left auricle by the pulmonary veins. From this cavity it passes into 

 that of the left ventricle, from which the cycle once more begins. 



The course of the blood from the left ventricle through the body generally to 

 the right side of the heart constitutes the greater or systemic circulation, while its 

 passage from the right ventricle through the lungs to the left side of the heart is 

 termed the lesser or pulmonary circulation. 



FIG. 410. Front view of the thorax, showing relation of the heart, lungs, etc., to the ribs and sternum. 

 P. Pulmonary orifice. Ao. Aortic orifice. M . Left auriculoventricular orifice. Tr. Right auriculoventrieular 

 orifice. 



It is necessary, however, to state that the blood which circulates through the 

 spleen, pancreas, stomach, small intestine, and the greater part of the large intes- 

 tine is not returned directly from these organs to the heart, but is collected into 

 a large vein, termed the portal vein, by which it is carried to the liver. In the 

 liver this vein divides, after the manner of an artery, and ultimately ends in capil- 

 lary vessels, from which the rootlets of a series of veins, called the hepatic veins, 

 arise; these carry the blood into the inferior vena cava (postcava), whence it is 

 conveyed to the right auricle. From this it will be seen that the blood contained 



