514 GREAT VESSELS OF THE HEART. 



From the course of these different vessels round the basis of 

 the ventricles of the heart, they are generally called Coronary 

 Vessels : the arteries are denominated, from their position, Right 

 and Left Coronary. 



The nerves of the heart come from the cardiac plexus, which 

 is composed of threads derived from the intercostal or great 

 sympathetic nerves, and the nerves of the eighth pair. 



Of the Aorta, the Pulmonary Artery and Veins, and the 

 Vena Cavce ; at their commencement. 



The two great arteries, which arise from the heart, commence 

 abruptly, and appear to be extremely different in their composi- 

 tion and structue from the heart. 



They are composed of a substance, which has a whitish 

 color, and very dense texture, and is very elastic as well as 

 firm and strong. 



When the pericardium is removed, these arteries appear to 

 proceed together from the upper part of the basis of the heart : 

 the pulmonary artery being placed to the left of the aorta with 

 the left auricle on the left side of it, and the right auricle on 

 the right side of the aorta. The pulmonary artery arises from 

 the most anterior and left part of the basis of the right ven- 

 tricle, and proceeds obliquely backwards and upwards ; 

 inclining gradually to the left side for about eighteen or 

 twenty lines ; when it divides into two branches which pass to 

 the two lungs. 



The aorta arises from the left ventricle, under the origin of 



veins of the heart into all the cavities of that organ, and particularly into the 

 Left Ventricle. But it was only in subjects with diseased lungs that this was 

 practicable. 



The existence of this communication between the coronary vessels and the 

 great cavities of the heart seems therefore to be proved. The easy demonstra- 

 tion of such subjects is ingeniously referred by Mr. Abernethy, to the obstruc- 

 tion of the circulation in the lungs ; and he regards the communication as a 

 provision enabling the coronary vessels to unload themselves, when the coronary 

 vein cannot discharge freely into the right auricle.* 



* This assertion of Mr. Abernethy's, lias not been confirmed by subsequent investigations, 

 except incases where the tissue of the heart was softened, and its vessels had been ruptured 

 by the force of the injection, p. 



