510 LEFT VENTRICLE. 



the cavity, and is situated on the left side of the pulmonary 

 artery. 



This auricle is lined by a small membrane, from which the 

 valves between it and the ventricle originate ; but it has no 

 fleshy columns or musculi pectinati, except in the angular pro- 

 cess properly called auricle. 



These valves and the ^orifice communicating with the 

 ventricle, resemble those which have been already described 

 between the right auricle and ventricle : but with this differ- 

 ence, that the valvular ring is divided into two portions only, 

 instead of three which are called Valvula Mitrales.* The 

 tendinous threads, which are connected to the muscular 

 columns, are also attached to these valves, as in the case of the 

 right auricle. 



These valves admit the passage of blood from the auricle into 

 the ventricle, but completely prevent its return when the 

 ventricle contracts. One of them is so situated that it covers 

 the mouth of the aorta while the blood is flowing into the ven- 

 tricle, and leaves that orifice open when the ventricle contracts, 

 and the passage to the auricle is closed. 



The Left Ventricle is situated posteriorly, and to the left of 

 the Right Ventricle. Its figure is different, for it is rather coni- 

 cal, and it is also longer. 



The internal surface of this ventricle resembles that of the 

 right ventricle : but the columnae carneae are stronger and 

 larger. 



On the right side of this ventricle is the mouth of the aorta. 

 The surface of the ventricle near this opening is smooth and 

 polished, to facilitate the passage of the blood. 



The mouth of the aorta is furnished with three semilunar 

 valves, after the manner of the pulmonary artery, but the 

 former are stronger ; the corpuscula Arantii are better developed 

 in them. Indeed, Mr. Hunter does not admit of their existence 

 in the pulmonary artery. The sinuses of Valsalva are about the 

 same size m both arteries. 



* From a resemblance in shape to the mitre or bishop's cap. P. 



