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PHYSIOLOGY. 



capillary plexus in the liver. This accessory circulation is commonly 

 designated as the portal circulation. 



From the right auricle the blood flows into the right ventricle, 

 from which it is expelled through the pulmonary artery to the lungs, 



Fig. 68. Diagram of the Circulation. (DuvAL.) 



1, Left ventricle. 2, Left auricle. 3, Right ventricle. 4, Right auricle. 5, 

 Aorta. 6, Systemic capillaries. 7, Inferior vena cava. 8, Pulmonary artery. 9, 

 Pulmonary capillaries. 10, Pulmonary vein. 11, Gastric and intestinal vessels. 

 12, Intestine. 13, Portal vein. 14, Portal vein, forming second capillary system 

 in the liver. 15, Liver. 16, Hepatic vein. 17, Pulmonary, or lesser, circulation. 

 18, Systemic, or greater, circulation. 



to be returned to the left auricle as bright-red, pure blood. This 

 change in color is due to the presence of oxygen in the haemoglobin 

 gained during the process of aeration. This shorter circuit is 

 known as the lesser, or pulmonary, circulation. 



Difference of pressure between the blood of the aorta and pul- 

 monary artery, on the one hand, and that in the venae cava? and 



