ACUTK KNDOCARDITIS IN THK HOKSK. 121 



exceedingh' infective, and its real nature is often misinterpreted, until! 

 after death. 



In animals, the changes shown by the endocardium after acute 

 inflammation are very diversified. On reading reported cases of " acute 

 endocarditis " in journals, it is clear that in many instances the changes, 

 noted do not justify the signification attributed to them. Cases have 

 been published under this title in which the existence of endocarditis, 

 was in no way demonstrated, even by the lesions. 



The diffuse reddening of the serous membrane, the ecchymoses,. 

 the irregular blackish patches, even the little fibrinous grains which 

 have been found, are by no means sufficient indications on which to- 

 base the diagnosis of acute endocarditis. Diffuse reddening of the endo- 

 cardium results from staining with altered haemoglobin, derived from red 

 blood-corpuscles destroyed during the course of certain infectious pro- 

 cesses. The other lesions are not infrequently seen in horses which die 

 from over-exertion, especially in extremely hot weather. They also occur 

 when death is preceded by violent struggling and long-continued agony. 



In the ordinary form of acute endocarditis the serous membrane is 

 thickened or elevated in places, has lost its polished appearance, is 

 covered with little, friable, greyish or reddish vegetations, at times 

 capped with a fibrinous layer, and marked at the seat of these lesions 

 and for some distance round them by fine branching vessels. There is 

 nothing more. These lesions sometimes extend over a considerable 

 portion of the endocardium ; they commonly affect the valves, and are 

 there always most marked. They are generally confined to the left 

 heart. The mitral and aortic valves are swollen, irregularly thickened, 

 often covered with little sessile vegetations adherent to and continuous, 

 with the membrane, some greyish in colour, others of a light red ;. 

 sometimes very small, very numerous and almost confluent ; they give 

 the membrane a roughened appearance. In the specimen I exhibit,, 

 you see they are collected at a short distance from the free border of 

 the valve. In many cases they first appear in the vascular portion 

 of the valves, and extend thence towards the free margin ; where 

 they attain the free edge of the valves the endocarditis is termed 

 marginal. The abnormal coloration is not removed by washing, and 

 closer examination of the patches, especially of their circumference, 

 reveals little vascular loops ; but the reddish-brown or blackish tints 

 which appear so rapidly in inflammation of richly vascular organs are 

 rarely seen. The majority of these vegetations are covered with a 

 fibrinous deposit seldom very adherent. On removing it the serous, 

 membrane appears superficially eroded. 



