1088 Valvular Diseases. 



transformed into thick flat pads, the separate portions of the 

 bicuspid and tricuspid valves into thick, knobby formations; 

 in exceptional cases contiguous parts of valves become adherent. 

 The thickened chordae tendineae appear shortened. On the 

 parietal layer of the endocardium changes are frequent but 

 less striking and only rarely produce thickening. 



If the atrophy of the valves or of the chordae tendineae 

 has advanced to such a degree that the extended valves no 

 longer touch, the result is an insufficiency, but if polypoid or 

 cauliflower-like deposits have formed on the valves or if the 

 latter are very rigid, and their contiguous portions perhaps 

 adherent, the result is a stenosis of the respective ostium. 

 According to the nature and localization of the changes a 

 stenosis is often present together with an insufficiency. The 

 portion of the heart which is proximal to the diseased part 

 (in the direction of the blood stream) is then dilated and more 

 or less hypertrophic. During the stage of incompensation 

 there exist symptoms of blood-stasis. 



As regards the seat of the changes the disease affects in 

 horses frequently the aortic valves (according to French 

 authors this is the most frequent form of heart trou])le in 

 horses), more rarely the bicuspid valve. In cattle and goats 

 the valves of the right heart are as a rule affected most fre- 

 quently, in swine those on the left side of the heart, especially 

 the bicuspid valve. In dogs mitral insufficiency is observed 

 most often, then the simultaneous affection of bicuspid and 

 tricuspid valves and about half as often disease of the tricuspid 

 valve alone. According to Larcher and Hartl the valves of the 

 right ventricle are usually affected in birds. 



Symptoms. According to the localization of the morbid 

 process the symptoms are so different that it appears proper 

 to consider them separately. 



(a) Insufficiency of the Aortic Valves. 



In insufficiency of the semilunar valves of the aorta a 

 slit-like opening persists between the valves during ventricular 

 systole, in consequence of which a portion of the blood which 

 had been forced into the aorta during the preceding systole 

 flows back into the left ventricle, producing a murmur in so 

 doing. At the same time blood flows into the left ventricle 

 from the left auricle, and the ventricle, receiving blood from 

 two directions, is dilated, owing to its power of adaptation, 

 but forces out its entire blood content during the next systole, 

 for which a stronger contraction is necessarily required. The 

 continuous increase in the activity of the heart gives rise to 

 a hypertrophy of the wall of the dilated ventricle. 



The symptoms of insufficiency of the aortic valves are as 

 follows: The stronger contraction of the hypertrophied and 



