MYOCARDITIS. 



151 



neither of these forms of chronic inflammation of the myocardium is 

 there a murmur unless a valvular lesion simultaneously exists, or 

 unless the auriculo-ventricular valves are imperfectly controlled in 

 consequence of weakness of the papillary muscles. In some cases 

 percussion reveals enlargement of the area of cardiac dulness due to 

 relaxation of the walls of the heart, and, in granulo-fatty myocarditis, 

 to dilatation of these cavities, in fibrous myocarditis to hypertrophy 

 of the left ventricle. But, as in the acute form, this symptom is 

 difficult of detection. 



If the animals are kept, the symptoms become continuously aggra- 

 vated, and may be supplemented by respiratory and gastric troubles 

 of reflex character. These are later complicated by disturbance due 

 to slowing of the circulation and weakness of the heart, vascular stasis, 

 engorgement of the lung and of other viscera, dropsy, oedema, and 

 finally by changes which indicate exhaustion of the heart. Degenera- 

 tive myocarditis marks the last phase in the series of disorders pro- 

 duced by valvular lesions. The successive changes seen during the 

 disease originate in the endocardium ; they end in degeneration of the 

 myocardium . 



Cortical or partial myocarditis produces much less pronounced 

 and much vaguer symptoms. In the horse it is sometimes only 

 indicated by intermittency. 



Chronic myocarditis always takes a very slow course ; it continues 

 for years, gradually becoming more marked, though it may for a time 

 remain stationary. It never tends towards recovery, however. If 

 the patients are kept, death follows from increasing feebleness and 

 wasting, or unexpectedly from syncope or rupture of the heart. The 

 ass whose case I described was found dead in its stall, without having 

 stopped work a single day, and without having shown any serious 

 respiratory trouble, despite the fact that in its case myocarditis was 

 complicated with disease and insufficiency of the aortic valves. 

 Rupture of the heart is very rare in all animals, though it may occur 

 under the influence of excessive excitement, or of a fall, or violent 

 effort during work. The heart then contracts with excessive energy, 

 the intra-cardiac pressure suddenly increases, and the muscular wall 

 having undergone degenerative change yields at its weakest point — 

 oftenest in one of the ventricles, at the seat of an aneurism, or of some 

 fatty or fibrous alteration. 



The diagnosis of myocarditis is surrounded with many difficulties. 

 In all species of animals mistakes are difficult to avoid, and diagnosis 

 should be delivered with great circumspection. The disease is sug- 



