DILATATION OF THE HEART. 



Result of obstruction to circulation. In right ventricle usually. In 

 auricle from narrow auriculo ventricular opening. Pure dilatation from 

 sudden extreme blood pressure as in inflammations of the lungs. In fat cattle 

 from fatty obstructions around the heart and great vessels. Weakness of 

 cardiac muscles in fatty degeneration, fevers, debility, etc. Symptoms : 

 dyspnoea under slight exertion, unsteady walk, coM, dropsical limbs, venous 

 pulse, pulse small, weak, irregular, intermittent, with palpitations. Treat- 

 ment : in early stages arrest the causes, arsenic, digitalis, fatten for butcher. 



Dilatation of the right cavities of the heart is one of the most 

 common heart diseases of the horse. It is an almost constant 

 condition in the emphysema of advanced broken wind (heaves), 

 and is a frequent concomitant of hypertrophy and an occasional 

 one of atrophy of the heart. Its usual direct cause is some 

 obstacle to the free escape of blood from the cavity affected. 

 Thus in broken wind, the difficulty of the circulation through the 

 lungs causes accumulation in the pulmonary artery and right 

 ventricle of the heart, the walls of which are distended because 

 of the unwonted internal pressure. When the dilatation of this 

 ventricle reaches a certain stage the auriculo- ventricular opening 

 is equally widened, the valves become insufficient to close it and 

 the right auricle and venae cavse participate in turn in the in- 

 ternal pressure and dilatation. The right ventricle is more often 

 affected than the left, because of the greater frequency of ob- 

 struction in the circulation through the lungs than in that 

 through the general system, and because of the thinness of its 

 walls which more readily give way under internal pressure. 

 Dilatation may result from disease of the great arteries, from 

 diminution of their calibre by the pressure of tumors, or by nar- 

 rowing of their openings at the heart, whether as the result of 

 diseased valves or other morbid condition. As affecting the 

 auricles primarily its usual cause is narrowing of the auriculo- 

 ventricular opening from some abnormal deposit. The extreme 

 thinness of the walls of the auricles allows these to give way 

 under internal pressure, even much more readily than the right 

 ventricle. 



The causes it will be seen are similar to those inducing hyper- 



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