Human physiology : designed for colleges and the higher classes in schools and for general reading . rom all parts ofthe body, at length are all united into two veins, which emptytheir contents into the heart. But there is a very remarkableexception to this. The veins which collect the blood from theviscera in the abdomen unite in one large trunk, called the venaportse; and this, instead of pouring its contents into the largevein that goes up to the heart, divides, like an artery, intobranches, which take all this Hood to the liver for the manufac-ture of bile. Fig. 24 represents this circulat
Human physiology : designed for colleges and the higher classes in schools and for general reading . rom all parts ofthe body, at length are all united into two veins, which emptytheir contents into the heart. But there is a very remarkableexception to this. The veins which collect the blood from theviscera in the abdomen unite in one large trunk, called the venaportse; and this, instead of pouring its contents into the largevein that goes up to the heart, divides, like an artery, intobranches, which take all this Hood to the liver for the manufac-ture of bile. Fig. 24 represents this circulation of the venaportse. 1, 1, are the veins coming from the intestines ; 2 is thetrunk of the vena porlae ; and 3, 3, are the branches of it dis-tributed in the liver. Now, it can not be pretended that thesuction power of the heart extends its influence through the veinsthat bring the blood from the liver, then through the capillariesof this organ, and then through all the veins that bring the THE CIRCULATION. 71 Circulation in the liver. Why the veins are full and the arteries empty after CIRCULATION OF VENOUS BLOOD IN THE LIVER. blood to the liver, even to the capillaries of the abdominal vis-cera. There must be, in this case, some propelling power inthe capillaries, and some, too, also in the veins. If there werenot, another subordinate heart would obviously be needed inthe vena portse, to pump up the blood from all the veins of theabdominal viscera, and then to send it through all its branchesinto the capillaries of the liver. 109. The veins have a less active agency in the circulationthan any of the other parts of the apparatus. It is for thisreason that commonly after death the veins are found quitefull of blood, while the arteries are nearly empty. The appa-ratus of the circulation may be regarded as forming a circle oforgans in this order—the heart, the arteries, the capillaries, andthe veins. The blood is constantly going the rounds of thiscircle. It is plain
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