Diseases of the Heart and Organs of Circulation. 403 



the horn or the depth and spring of the rib. The lower animals 

 are further subject to congenital malformations and imperfections 

 and to deposits of morbid material around the heart or in its sub- 

 stance so as to impair its healthy action. 



Horses and dogs have special predisposing causes in the violent 

 and prolonged exertion to which they are habitually exposed. 

 The quiet sluggish and non-excitable ox and pig meet with dan- 

 gers no less real, though of a different kind, in the overfeeding 

 which induces fatty degeneration of the heart as of other 

 muscular tissues. The larger ruminants are further endangered 

 by their propensity to swallow needles and other sharp pointed 

 bodies which ultimately reach and penetrate the heart. 



The prevalence of heart disease in animals may /be deduced 

 from the fact, that out of 150 horses, oxen and dogs dissected at 

 Montfaufon by Leblanc in 1840, not less than one- twentieth, pre- 

 sented cardiac lesions. The supposition of an immunity of the 

 lower animals, has been largely due to the heavy muscular 

 shoulder of quadrupeds, which covers the upper and anterior 

 regions, of the heart, shutting them out from physical exploration. 

 In man the entire heart and connecting blood vessels are so\open 

 to examination, that the physician can pronounce with\ the 

 greatest accuracy, not only concerning the existence of disease, 

 but also its precise locality and nature. In the quadrupedlno 

 such facility is open to us, and veterinarians have too generally 

 refused to face the di£&culty, preferring to ignore heart diseases, 

 or still worse seeking to cover their ignorance by the assertion 

 that such affections rarely exist. Now, however, we not only 

 know that heart diseases are much more frequent in the lower 

 animals than heretofore believed, but that as a general rule they 

 are suflSciently manifested and recognizable by their distinctive 

 symptoms. 



Position and exposure of the heart. In the horse the heart 

 has only its apex and a small portion of its left ventricle ap- 

 proached to the surface of the chest, at a point where it is felt to 

 beat behind the left elbow. The apex approaches the surface in 

 the interval between the fifth and sixth ribs and close above the 

 breast bone. The posterior border of the ventricle follows a nearly 

 vertical line upwards from this point, while the anterior border 

 has a direction upward and forward crossing diagonally over the 



