SEMILUNAR VALVES THE AORTIC ORIFICE. 359 



treating the subject, but shall thus have less to repeat, and, moreover, 

 less to retract, than by any other mode. As the pathogeny of valvular 

 defect of the aorta is much more simple than that of mitral disorder, 

 as its symptoms are easier of comprehension, and as its consequence? 

 are much longer and better withstood than are those of mitral defi- 

 cience, we shall first take up the subject of aortic valvular disease. 

 Derangement of the valves is of far less common occurrence in the 

 right than in the left heart, so that we shall reserve the discussion of 

 the former until the last. 



CHAPTEK VI. 



INSUFFICIENCE OF THE SEMILTTNAK VALVES, AND CONSTRICTION OF 

 THE AORTIC ORIFICE. 



ETIOLOGY. Closure of the semilunar valves takes place in a man- 

 ner purely mechanical, while a certain vital action is required to effect 

 closure of the valves between ventricle and auricle, namely, contrac- 

 tion of the papillary muscles. If the mere pressure of the blood during 

 diastole of the left ventricle do not suffice to deploy and press together 

 the leaves of the semilunar valve, which were pushed up against the 

 wall of the aorta during systole, there will be regurgitation of blood 

 into the ventricle, and the valve is insufficient. If, however, during 

 systole, the semilunar valves do not yield to the current of the blood, 

 and lie back against the aortic wall as it emerges from the left ven- 

 tricle, but stand projecting into its outlet, we have constriction (steno- 

 sis). Much more rarely the latter occurs from contraction of the aorta 

 at the point of insertion of the valves, whereby the outlet is dimin- 

 ished. 



The alterations which cause insufficience and constriction of the 

 aortic valves are the results of inflammation, but less often of endocar- 

 ditis, which we have described in Chapter IV., than of a more chronic 

 form of inflammation, which attacks the arteries, and whose results are 

 known as atheroma of the arteries. Hence it follows, although not 

 without exception, that valvular disease of the aorta is found at a more 

 advanced period of life, when arterial atheroma is far more frequent 

 than during youth, and that its development is more slow and gradual 

 than that of the disorders caused by endocarditis. 



ANATOMICAL APPEARANCES. If, upon autopsy, we remove the 

 neart and aorta ; and if, upon filling the latter with water sufficient to 

 distend its walls, the water flow into the ventricle because the edges 

 of the valves do not touch, we may assume that such regurgitation has 

 also occurred during life, and must regard the valves as insufficient. 



