XXII.— MYOCARDITIS. 



In animals, and particularly in the horse, inflammation of the 

 myocardium, either acute or chronic, is much more frequent than 

 might be supposed from the small number of published cases. Our 

 present knowledge on this subject is still very defective, especially from 

 the clinical point of view, because, as I shall almost immediately show 

 you, myocarditis is characterised by less striking symptoms than 

 endocarditis and pericarditis, and because many cases having only been 

 diagnosed on post-mortem examination, the observers have necessarily 

 been restricted to describing the anatomical lesions. 



The specimens which I place before you may be separated into 

 two groups : one, illustrating the changes in acute myocarditis, are 

 derived from horses dead of various infectious diseases, — usually, how- 

 ever, contagious pneumonia ; the others, showing lesions of chronic 

 myocarditis, have almost all been obtained during post-mortem exami- 

 nation of animals used for the exercises in practical surgery. 



Among these are two in which the anatomical and pathological 

 characteristics of the two great varieties of myocarditis are typical, 

 though excessively pronounced. 



First of all I show you the heart of a horse dead of contagious 

 pneumonia on the eleventh day, in which gangrene of both pulmonary 

 lobes existed as a complication. It is very large — weighs more than eight 

 and a half pounds, and has been the seat of acute diffuse myocarditis. 

 It shows large yellowish patches, irregularly distributed, but principally 

 occupying the left ventricle and auricle. On the left ventricle, starting 

 from the auriculo-ventricular furrow, is a large zone of fatty degenera- 

 tion, measuring from one and a half inches to three inches in width, 

 according to the point selected, and sharply differentiated from 

 adjacent tissues by its yellow colour. Sections through the wall and 

 cardiac septum vary in colour from brown to red, grey, or yellow, 

 according to the point chosen. Small hsemorrhagic centres also exist. 

 Several large areas of degeneration extend through the entire thickne>=s 



