CIRCULATION 



233 



pouches attached along their curved margin to the walls of the 

 artery and upper part of the ventricle, and with their concavities 

 directed away from the ventricle. In the centre of the free 

 margin is a fibrous thickened nodule, the corpus Arantii, from 

 which a very thin piece of membrane, the lunule, extends to 

 the attached margin of the edges. A pouch, the sinus of 

 Valsalva, lies behind each cusp. 



The arrangements of these various cusps is of importance in 

 connection with their action (fig. 110). 



Aortic Valve. The anterior cusp is largest, and lies some- 



Dp.msp. 



Dp 



FIG. 111. Relations of the Thoracic Viscera in the Horse. C., heart; Dp., 

 the diaphragm ; exsp. , in expiration ; insp., in inspiration. (From 

 ELLENBERGER.) 



what deeper in the heart than the others. At each side it is 

 attached to the aortic wall, but below it is attached to the 

 upper part of the septum ventriculi, so that the base of the 

 sinus of Valsalva is formed by the upper part of the septum. 

 At a somewhat higher level is a cusp which is. partly attached 

 to the upper part of the septum, partly to the posterior wall 

 of the aorta, where this becomes continuous with the anterior 

 cusp of the mitral. The third cusp is still higher, and is 

 attached to the aortic wall, where it becomes continuous with 

 the anterior cusp of the mitral. 



