150 CLINICAL vete:rinarv medicine and surgery. 



valvular endocarditis they are almost always localised near the auriculo- 

 ventricular or arterial openings. The process extends from the base of 

 the valves into the adjacent zone of muscle, and thus may produce 

 so-called ''annular" myocarditis. Through the medium of the cJwi'dcr 

 tendinccc it may extend to the iiiuscuH papillares, and end by transforming 

 them almost entirely into iibrous cords. Similarly in pericarditis, 

 secondary localised myocarditis is sometimes seen in certain parts of 

 the superiicial layers of the muscle. 



Localised myocarditis, followed either by fibrous or fatty degenera- 

 tion, may weaken the ventricular wall until it yields to the pressure of 

 blood, and finally undergoes saccular dilatation, producing a partial 

 chronic aneurism. 



Bearing in mind the functional importance of the heart, and the 

 grave nature of the lesions described, it might be expected that 

 chronic myocarditis would produce very marked symptoms clearly 

 indicating its existence. On the contrar}^, however, the disease often 

 continues unperceived for months or even years, its stages succeeding 

 one another very slowly. When chronic myocarditis appears as a 

 primary condition, animals can often be kept at their usual work for 

 a long time ; and even when it succeeds to the acute form, they are 

 able to return to work after termination of the latter. 



In either case a time arrives when the previously latent disease 

 produces disturbance which can no longer be ignored. The most 

 ordinary is that complex condition known as broken wind, especially 

 marked by dyspnoea. At work, difficulty in breathing soon occurs, the 

 heart's action becomes strong and tumultuous, and true palpitation is 

 perceptible on applying the hand over the precordial region. In some 

 cases the horse stops suddenly during work, and is often thought to 

 be suffering from colic, but in animals angina pectoris, like vertigo, 

 fainting, and syncope, appears to be rare. During this preliminary 

 period, which has been described as irritative, palpitation of the heart 

 and acceleration of the pulse can be detected, even when at rest in the 

 stable. 



With the lapse of time, dyspnoea increases during work, occurring 

 in paroxysms, while the heart's action becomes modified and the pulse 

 weak, infrequent, and intermittent. Not only does palpitation cease, 

 but the contractions of the heart may be weaker than normal, and, 

 like the pulse, infrequent, irregular, and intermittent. On ausculta- 

 tion, the heart-sounds are rather attenuated in granulo-fatt}' myo- 

 carditis, but prolonged and accompanied by a rolling or double sound 

 in sclerosing myocarditis, with hypertrophy of the left ventricle. In 



