126 



CLINICAL VETERINARY MEDICINE AND SURCIERV. 



changes ending in insufficiency. These changes may assume very 

 varying anatomical appearances. You may judge of this by examining 

 the specimens I place before you. Sometimes the valves are simply 

 thickened, rigid, wrinkled, and shrivelled ; sometimes they show losses 

 of substance, giving them a reticulated or fenestrated appearance ; in 

 some cases they exhibit aneurismal dilatations, projecting above the 

 surface of the heart, the wall of the aneurism being either intact or 

 perforated ; in others, again, they are fungous and covered with pea- 

 like or strawberry-like vegetations ; finally, they may contract adhe- 

 sions one with the other, or with adjacent tissues. Usually these 

 lesions are unequally marked on the three valves ; sometimes they 



Fig. 1 6. — Chronic endocarditis of the aortic valves. 



only affect one, though even in this case they may be very pro- 

 nounced. 



The valves never close completely, an opening of varying form 

 and size remaining between them through which blood regurgitates. 

 When the aortic ring has not been divided the insufficiency can 

 readily be detected. After removing its lower third, one has only to 

 place the heart in a vertical position, and to pour a little water into the 

 aorta ; the valves no longer closing exactly, liquid escapes by the space 

 between the valves, and passes into the ventricle. 



These changes in the aortic opening are always accompanied by a 

 certain degree of hypertrophy of the left ventricle, consequent on 

 insufficiency, and due to a very simple mechanism. After each systole, 

 the blood injected into the aorta, which should be retained by closure 

 of the semilunar valves, returns in part into the ventricle. This 

 returned blood being added to that coming from the auricle, two 

 abnormal conditions successivel}' arise ; the ventricle dilates excessively, 



