198 DISEASES 01^ THE HE ART. 



constitute what may be called a beat, is the same as 

 described by Laennec : viz. 1. The ventricular systole 

 occupies half the time, or thereabouts, of a whole beat. 

 2. The ventricular diastole occupies a fourth, or at most a 

 third. 3. The interval of ventricular repose occupies a 

 fourth, or rather less, during the latter half of which the 

 auricular systole takes place.^^ 



This brief exposition, from Dr. Hope, of the action of 

 the heart, will prepare us for that practical study of its 

 movements in a state of health which it is absolutely 

 necessary for us to institute before we can take due 

 cognisance of those present under disease. Laennec directs 

 this study to be conducted under four views or heads : — 

 1. The extent over which the actions of the heart can be 

 heard. 2. The shock or impulse communicated. 3. The 

 nature or intensity of the sound. 4. The order or rhythm. 

 In our examination we must take care that the animal be 

 in a state of perfect quietude, and entirely free from any 

 suspicion or alarm concerning our presence or doings with 

 him. 



The extent to which the sound of the hearths action is 

 audible will vary, even in health, according to the make 

 and embonpoint of the subject under examination. In lean 

 and narrow-chested horses it may be heard upon the right 

 as well as upon the left side, and upon the latter over a 

 large superficies : on the other hand, in such as are circular- 

 chested and fat, the sound will be confined to the left side, 

 and to the spot directly opposite the heart. Exercise or 

 agitation of any kind will augment the sphere of sound ; 

 and during those violent beats of the heart called palpu 

 tation, their influence will extend even beyond the chest, 

 to other parts of the body. " By hyj^ertrophy , the impulse 

 is increased, but the sounds diminished." — "By dilatation, 

 the impulse is diminished, often to the extent of being 

 imperceptible.'' " By hypertrophy with dilatation, the 

 contractions of the ventricles give a strong impulse'' — 

 '* abrupt, dead, violent blows, which strongly repel the hand.'^^ 



' For most valuable inforuiation on tliese points consult Laennec and Hope. 



