212 DISEASES OF THE HEART. 



affects one ventricle without the other/^ — "Dilatation of 

 the auricles scarcely ever exists without more or less thick- 

 ening of their parietes/' We must take care to distinguish 

 between distension and dilatation of the cavities. " When 

 merely distended, they are found enlarged, firm, and tense; 

 but these conditions almost entirely disappear when the 

 blood is pressed out through their natural apertures. On 

 the contrary, when truly dilated, they have no appearance 

 of tension, are more or less flaccid, and the enlargement 

 persists after the blood has been evacuated/^ ^ 



Dr. Copland makes the following pertinent observations 

 on the subject. "When the auricles are protected by a 

 natural state of their valves, and of the auriculo-ventricular 

 orifices, the ventricles may be dilated without the former 

 being materially affected ; but when the auricular valves are 

 diseased, so as to occasion interruption to the passage of the 

 blood from the auricles, or when the auriculo-ventricular 

 openings are dilated, so as to permit regurgitation from the 

 ventricles, then the auricles become dilated, although rarely 

 without some increase in the thickness of their parietes.'^ 

 Dr. Hope has, with truth, remarked that "change in the 

 capacity of the cavities of the heart may result, not only 

 from obstacles in the circulation, but also/rom debility.'' 



Leblanc mentions a case of dilatation of all four cavities 

 of the heart of a horse. Yezelesse gives an account of a 

 heart of enormous volume : it measured a foot from base to 

 point, and ten inches from point to summit of the ventricles; 

 its parietes were weakened by attenuation, and several of its 

 fleshy columns lacerated. MM. Riss and Meyer have pub- 

 lished a case of dilatation with rupture of the right auricle 

 of the heart of a horse : the cavity was at least double its 

 ordinary amplitude, and its walls attenuated to that degree, 

 that, in the place where the rupture took place, they were 

 not thicker than a sheet of paper. 



One of the best accounts of dilatation the veterinary- 

 annals of this country afford, is contained in a case commu- 

 nicated to The Veterinarian, in 1834, by Mr. Pritciiaru. 

 ' From section i, chapter ii, of Dr. Hope's Treatise. 



