190 MANUAL OF EQUINE MEDICINE. 



In many cases, where the hypertrophy is compensatory, 

 there are no symptoms. When the hypertrophy is consider- 

 able and in excess of the dilatation, the arteries tend to 

 become fuller, the veins less full, and the circulation is 

 accelerated. The pulse, at first full, becomes feeble as the 

 dilatation increases. 



The impulse of the heart is increased and is sometimes 

 prolonged; and in very marked hypertrophy is often 

 observable at a distance from the animal, and may be 

 distinctly felt. 



The heart-sounds may be more intense, but are usually 

 less distinct. 



When dilatation is in excess, the veins tend to become 

 over full, the arteries less full, and the circulation retarded. 

 The pulsations are smaller, feebler, and more irregular or 

 intermittent ; and there may be dyspnoea, especially when 

 exertion is made. In advanced stages there is coldness of 

 the extremities, and a tendency to oedema or dropsical effu- 

 sions. The jugular venous pulse is most often noticed 

 when the right side is dilated. So long as the hypertrophy 

 keeps pace with dilatation there may be no symptoms ; but 

 when the hypertrophy ceases to progress, while the dilata- 

 tion increases, symptoms are soon manifested from impair- 

 ment of the heart's action. Exertion in this case is attended 

 with much difficulty. 



Morbid Anatomy. — The heart is increased in weight and 

 bulk, the relative extent of which depends upon the relation 

 between the hypertrophy and the dilatation. The shape is 

 also often modified according to the parts involved, and is 

 generally rounder than natural. The auricles are much 

 less frequently enlarged than the ventricles, and the left 

 ventricle more often than the right. 



ATROPHY OF THE HEART. — Atrophy, or decrease of 

 substance of the heart from diminution in the size or in the 



