BIGHT AURICLE. 



505 



ventricle; and from this ventricle arises the artery denomi- 

 nated Fidmonary, which passes to the lungs. 



The Pulmonary veins, which bring back the blood from 

 the lungs, open into the left auricle ; this auricle opens into the 

 left ventricle ; and from this ventricle proceeds the Aorta, 

 or great artery, which carries blood to every part of the 

 body. 



The heart is preserved in its position, 1st, by the vena) cavae 

 which are connected to all the parts with which they are con- 

 tiguous in their course ; 2d, by the vessels which pass between 

 it and the lungs, which are retained in a particular position by 

 the mediastinum ; 3d, by the aorta, which is attached to the 

 mediastinum in its course downwards, after making its great 

 curve ; and 4th, by the pericardium, which is attached to the 

 great vessels and to the mediastinum. By these different 

 modes the basis of the heart is fixed, while its body and apex 

 are perfectly free from attachment, and only contiguous to the 

 pericardium. 



The external surface of the 

 heart, being formed by the serous 

 layer of the pericardium, is very 

 smooth : under this surface a 

 large quantity of fat is often 

 found. 



The two auricles are contigu- 

 ous to each other at the base, 

 and are separated by a partition 

 "0 which is common to both. 



The Right Auricle originates 

 from the junction of the two 

 venae cavae. These veins are 

 united at some distance behind 



Fig. 



127.* 

 ■ft- ?£ 



* Longitudinal section of the heart, showing its cavities, b, Right ventri- 

 cle, c, Septum ventriculorum. d, Right auricle, e, Left auricle. /, Section 

 of the mitral valves, g, Section of tricuspid valves, h, Arch of aorta, k, 

 Descending aorta, i, i, Vena cava superior and inferior, k, k, Right and left 

 branches of the pulmonary artery. I, I, Pulmonary veins. 



43 



