392 



VETERINARY PHYSIOLOGY 



Arantii, from which a very thin piece of membrane, the 

 luniile, extends to the attached margin of the edges. A 

 j)ouch, the sinus of Valsalva, lies behind each cusp. 



The arrangements of these various cusps is of import- 

 ance in connection with their action (fig. 167), 



(i.) Aortic Valve-- — -The anterior cusp is largest, and lies 

 somewhat 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 



Fig, 168, — Relations of the Thoracic Viscera in the Horse. C, heart ; Dp., 

 the diaphragm; exap., in expiration; insp., in inspiration; Venir,, 

 stomach ; SpL, spleen. (From Ellenbergek.) 



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. 



(ii.) Pulmonary Valve. — The posterior cusp is mounted on 

 the top of the septum ventriculi, and is at a somewhat lower 

 level than the other two. 



