196 MANUAL OF EQUINE MEDICINE. 



diate causes are over-exertion and shock, resulting from a 

 fall or from direct violence to the chest. 



It is of most frequent occurrence in aged horses, after 

 sharp exertion. 



The usual seat of the rupture is at the conus arteriosus of 

 the left ventricle, where the tendinous ring unites the great 

 aorta with the ventricle. 



Mr. Percival records an instance of rupture of the right 

 auricle in the horse occurring shortly after a race. 



NEW FORMATIONS IN CONNECTION WITH THE 

 HEART. — The new formations met with most commonly 

 in the heart of the horse are malignant and parasitic 

 growths, cardiac polypi, and vascular tumours. 



The effects of these growths on the health of the animal 

 vary chiefly in accordance with their situation, and also, but 

 to a less extent, with their nature. 



Occasionally the heart is the seat of malignant growths, 

 which though possibly originating in the organ itself, are 

 with greater probability regarded as sequels of the general 

 invasion of the system by cancerous growths. 



Hydatid cysts have been described in connection with 

 the heart in cattle and sheep, and they may also occur in 

 the horse. 



Single individuals of strongylus armatus have been found 

 in the pericardial sac of young horses by Professor 

 Robertson. 



Vascular tumours in the heart are due to dilatation of the 

 veins and capillaries beneath the endocardium. 



Of all cardiac growths, the most frequently met with are 

 the so-called fibrinous polypi, which seem to originate from 

 the muscular tissues of the heart. They are composed of 

 laminated fibrin, the central parts being more distinctly 

 organized and fibrillated. 



Cardiac tumours cannot be diagnosed during life. 



