358 RUPTURES OF THE HEART. 



five or six days. In the dog from one to three grains may be 

 prescribed, at similar intervals. Leblanc suggests the pro- 

 priety of very small doses, cautiously administered. 



In a practical point of view, the results of sudden efforts of 

 the heart, and which are by no means unfrequent, especially 

 in this country, where willing horses are pushed beyond their 

 strength, are next in importance. 



RUPTURES OF THE HEART AND OF THE VESSELS IN 

 ITS VICINITY. 



Without change in structure, the heart or great vessels 

 burst under the influence of undue exertion or violent con- 

 cussion. In man, from fatty degeneration, the substance of 

 the heart gradually gives way, but in the horse this form of 

 rupture is rarely seen. The most common seat of rupture I 

 have observed, and which occasionally proves the source of 

 death in a hard-contested race, or in a cart-horse drawing a 

 very heavy load up-hill, is laceration of the aorta from its 

 connexion with the left ventricle. The tendinous ring around 

 the semilunar valves snaps, hemorrhage ensues, and the ani- 

 mal dies. I have witnessed this accident in active Clydesdale 

 horses, in which the heart presented no organic lesion what- 

 ever. 



The next form of rupture is one which my brother has 

 described fully in his work on Researches in Pathological 

 Anatomy and Clinical Surgery. They are ruptures, the 

 result of violence, and occurring from falls, blows, or sudden 

 jerks. My brother says : 



"The mechanism of these traumatic heart ruptures deserves 

 consideration. With a view to explain it, Dr John Davy 

 instituted a series of seventeen experiments (Op. cit. p. 452-3) 

 on the dead bodies of men and animals, by tying the various 

 great vessels in the neighbourhood of the heart, and forcibly 



