466 DISEASES OF THE CIRCULATORY SYSTEM. 



grammes ; at its superior part it was hollowed by a large orifice, 

 like the openiug of a large shell, with which the vena cava corre- 

 sponds. The horse at the autopsy of which this lesion was found 

 was but eight years old ; for three years he had done excellent 

 draught service without ever showing any symptoms of uneasiness 

 before the last weeks of his existence. In less than two months he 

 became very thin and weak, to the extent of not being able to rise. 

 In most cases the ossification of the auricle of the heart does not 

 produce any serious trouble of the circulation, because it is limited 

 and isolated, without any concomitant lesioos of the orifices and 

 valves. It concerns the anatomo-pathologist much more than the 

 practitioner.] 



RUPTURE OF THE HEART. 



Etiology. Outside of the action of traumatisms, this accident is 

 caused by certain alterations of the myocardium which lessen 

 the resistance of the walls of the organ ; at times they simply 

 predispose to rupture, in other instances they end in occasion- 

 ing it. 



Among these alterations we must mention : inflammation, soft- 

 ening, abscess formation, weakening of the walls by cardio-sclerosi& 

 and aneurism, senile degeneration of the muscular fibres, endocar- 

 ditis and pericarditis, atheromatous degeneration of the base of the 

 aorta, echinococcus and the nematode worms (Spiroptera) located in 

 the walls of the heart, etc. The principal causes which determine 

 it are commotions of the trunk, violent falls (Hertwig), over-ex- 

 citement produced by coitus (Hering), the operation of ascites in 

 the dog (Stockfleth, and acute tympanites in the ox (Anacker, 

 Mayer, Perdan). 



Pathological anatomy. Besides the primitive alterations of 

 myocarditis, we find a more or less long tear in the wall of the 

 heart (3 to 4 centimetres on the average) ; it is mostly located upon 

 an auricle, at the base of the aorta, or of the pulmonary artery (see 

 Rupture of the Large Bloodvessels). The pericardium is distended 

 by a blood collection (hemo-pericardium). 



Symptoms. The tearing of the heart is announced by a sudden- 

 falling, which is apoplectiform ; in sinking, the horse sometimes 

 utters a piercing cry (Alers); in other cases the respiration becomes 

 very accelerated ; the animal, taken with vertigo, trembling, stag- 

 gers, drops, and presents symptoms of internal hemorrhage, and 



