DISEASES OF THE HEART IN DOMESTIC ANIMALS. 
257 
mares. I have even found that established defects of the valves 
improved after two years life of breeding; while the brood mare 
as a draught horse would surely have died. Among young horses 
which are being trained and broken, heart diseases occur propor¬ 
tionally more frequently than among older horses which have been 
in service. Nervously excited, timid animals have a particular 
predisposition to the disease. 
H cart diseases are also often directly or indirectly caused and 
determined by previons or still existing changes of other organs. 
Such pathological changes of other organs, which only exist in 
consequence of heart affections, are not to be confounded with the 
above named. Often the most efficient diagnosticians consider 
such changes the cause, whilst they are merely the results of heart 
diseases ; but in many cases a definite limit between cause and 
effect is not possible 
Affections of the heart are occasioned by the lateral pressure 
of the neighboring parts, by aggravated circulation, in the calling 
forth of the more violent heart affections, by swellings in the 
abdominal and thoracic cavities, by new formations from without 
or within. Here the influence of the aneurismatic pouches at the 
pulmonary artery and other vessels deserves particular attention. 
Changes and degeneration in the spleen and liver exercise a 
pressure upon the vessels of these organs, and consequently 
generate disturbances of the heart and circulation. The coagu¬ 
lation in the vessels is important for the aetiology of heart dis¬ 
eases ; for as soon as the coagulation exists in greater dimensions 
disturbances in the circulation arise, which, after continuance, 
have, as a result, chronic heart disease. 
Mechanical influences from without, such as too tight buck¬ 
ling on of the harness, a strong pressure of the girdle, exagger¬ 
ated checking of young training horses, frequently produces 
sudden heart affections, and if the causes continue they become 
plastic. The effort a young horse in training makes to free him¬ 
self from the harness which embraces his body, is often amazing. 
And the irrational trainer considers these exertions due to ill- 
temper, while they are nothing more than an impulse of self-pre¬ 
servation on the part of the animal, which, breathing heavily and 
