CIRCULATION OF THE BLOOD. 



53 



While there is but one circulation physiologists frequently divide the cir- 

 culatory apparatus into : 



1. The Systemic Circulation, which includes the movement of the blood 

 from the left side of the heart through the 



aorta and its branches, through the capilla- 

 ries and veins to the right side. 



2. The Pulmonary Circulation, which 

 includes the course of the blood from the 

 right side through the pulmonary artery, 

 through the capillaries of the lungs and 

 pulmonary veins to me left side of the 

 heart. 



3. The Portal Circulation, which in- 

 cludes the portal vein. This is formed by 

 the union of the radicles of the gastric, 

 mesenteric and splenic veins, and carries 

 the blood directly into the liver, where the 

 vein again divides into a fine capillary 

 plexus from which the hepatic veins arise 

 which empty into the ascending venae cavae. 



Movements of the Heart. At each 

 revolution, during the systole, the heart 

 hardens and becomes shortened in its long 

 diameter ; its apex is raised up, rotated on 

 its axis from left to right and thrown for- 

 ward against the walls of the chest. The 

 impulse of the heart, observed about two 

 inches below the nipple, and one inch to 

 the sternal side, between the fifth and sixth 

 ribs, is caused mainly by the apex of the 



heart striking against the chest walls, as- a, right, I, left auricle ; A, right, B, 



left ventricle ; i , pulmonary artery ; 

 2, aorta; /, area of pulmonary, 



SCHE ME OF THE CIRCULATION. 



sisted by the distention of the great vessels 

 about the base of the heart. 



K, area of systemic circulation; 

 o, the superior vena cava ; G, area 

 supplying the inferior vena cava, u; 

 d, d, intestine ; m, mesenteric ar- 

 tery ; q, portal vein ; L, liver ; h, 

 hepatic vein. From Landois. 



Sounds of the Heart. If the ear be 

 placed over the cardiac region, two distinct 

 sounds are heard during each revolution of 

 the heart, closely following each other and which differ in character. 



The sound coinciding with the systole in point of time, the first sound, 

 is long and dull, and caused by the closure and vibration of the auriculo- 



