109S Valvular Diseases. 



tion, while in aortic stenosis sjinptoms of cerebral anemia may- 

 exist. 



The anatomical changes afford a satisfactory explanation 

 why in diseases of the aortic ostium the sjanptoms of stasis 

 generally become manifest later than in other valvular diseases. 

 Not only is the most vigorous portion of the heart back of the 

 affected portion in this ease, but the weakening of the left ven- 

 tricle causes a notable stasis only in the lesser circulation, which 

 can moreover be compensated hj the right ventricle. If, on the 

 other hand, the right ventricle is obliged to compensate a heart 

 lesion, the stasis continues, immediately to the right auricle 

 and to the whole venous system, when the right ventricle be- 

 comes fatig-ued. Most unfavorable are conditions in diseases 

 of the right venous ostium because the thin-walled right auricle 

 is hardly capable of producing a compensation worth mention- 

 ing; in valvular diseases of the last variety a stage of com- 

 pensation can therefore hardly be considered. 



The cause of the permanent incompensation or decompensa- 

 tion which develops after a certain time can at present not be 

 explained satisfactorily for all cases. In a number of cases the 

 fact that the heart muscle is finally incapable of overcoming the 

 constantly increasing difficulties must probably be attributed to 

 the gradually increasing obstacles to the blood current. A 

 similar effect results from frequently repeated severe muscular 

 exertion, and from pulmonary edema which is not rare, espe- 

 cially in horses. In other cases the heart muscle is weakened 

 by myocardial inflammation which developed simultaneously 

 with or in consequence of the endocarditis. The strength of the 

 heart muscle is also reduced hy an extensive degeneration, while 

 a slight degree of degeneration is not important in this respect. 

 Finally, a functional disturl^ance of the heart muscle must be 

 assumed, in a considerable number of cases, to form the basis of 

 incompensation, which cannot at present be demonstrated his- 

 tologically. 



The incompensation is manifested by evidences of heart 

 weakness, that is, by lowered arterial pressure and by venous 

 stasis. The slowing of the blood current and the increased 

 fulhiess of the veins become manifest in the appearance of 

 cyanosis, especially a bluish-red discoloration of the mucous 

 membranes and even of the unpigTuented skin (especially in 

 hogs) ; sometimes dilatation and perhaps an undulating course 

 of the veins are also observed. The fullness of the jugular 

 veins is particularly striking and is not infrequently associated 

 with venous pulsations. Dropsical effusions into the body cav- 

 ities and edemas are further occurrences. Edematous swellings 

 appear first on the front and lower chest, on the lower abdomen 

 and in the lower portions of the extremities, although in the last 

 location they usually do not attain a considerable degree, owing 

 to the tightness of the skin, especially in large animals. In the 



