140 CLINICAL VETERINARY MEDICINE AND SURGERY. 



obstruction, which finally reacts on the left ventricle. In the lung the 

 useful respiratory surface becomes more and more reduced ; the 

 oedema, inflammation, and obliteration of capillaries steadily diminish- 

 ing the small number of pulmonary alveoli still capable of carrying on 

 oxygenation of blood. Toxic blood completes the disorganisation 

 produced by mechanical disturbance. The heart, already exhausted, 

 is arrested by the increasing asphyxia. 



At advanced stages of mitral disease death may occur rapidly by 

 another process. On account of the slowness of circulation coagula- 

 tion may occur in the arteries of organs essential to life. This explains 

 how patients sometimes die in a few days, in a few hours, indeed in a 

 few moments, either from thrombosis of the coronary arteries or from 

 thrombosis or embolism of the pulmonary artery. Sudden death, 

 however, is rarer than in aortic insufficiency. 



The diagnosis of mitral insufficiency offers little difficulty in the 

 horse. Tricuspid insufficiency (which is much less common) is almost 

 -always brought on by dilatation of the right heart, consequent on 

 chronic pulmonary affections, especially old-standing emphysema. It 

 is soon accompanied by a well-marked venous pulse, and the tricuspid 

 systohc murmur, usually softer, less prolonged than the mitral sound, 

 is also heard at a more anterior point. With a little practice, no 

 mistake need be made between this and the diastolic murmur of aortic 

 insufficiency. The presystolic murmur produced by mitral contraction 

 is extremely rare. 



What I have already said of the course of the disease will guide 

 you in prognosis, which is of extreme gravity. No improvement is 

 possible, nor can the development of the cardiac lesions or the accidents 

 which follow in their train be arrested. You have seen that irregularities 

 of the heart and pulse add to the gravity of prognosis. When they 

 appear, the heart has undergone a secondary change, either in its 

 muscular tissue or in its nervous apparatus. 



The treatment of mitral insufficiency is of little interest. As soon 

 as the compensation period is over, the animal is slaughtered, or 

 passes into fresh hands. 



Even when the disease is recognised in its eusystolic stage, before 

 actual organic change has occurred, the various drugs recommended 

 are useless. The most reasonable treatment consists of rest, moderate 

 exercise, and good hxgienic surroundings — treatment inapplicable to 

 working animals. 



At the asystolic stage the drugs indicated are those capable of 



