CARDIAC IMPULSE. 543 



ment in an upward and lateral direction ; this may occur from 

 collections of fluid in pericardium or chest, or from changes 

 connected with the great vessels at the root of the lungs. 



The space over which the impulse is defined may be en- 

 larged or diminished. It is increased in all cases of cardiac 

 hypertrophy, and those of structural change of the pericardium 

 with adhesions to the costal walls ; also, although of a feeble 

 and muffled character, where pericardial effusion exists. 



2. Force and Character. — {a) Increased impulse, impulse 

 more forcible and sometimes over a greater space than in 

 health, is detectable in many cases of structural change of the 

 heart itself It is well marked in most instances of hyper- 

 trophy with dilatation and valvular insupiciency, probably the 

 most common form of cardiac disease in the horse. In this con- 

 dition the character of the impulse is peculiar and rather 

 diagnostic ; it is not accomplished by a jerk, but is rather slow 

 and steady, occasionally giving the impression of being double 

 from its being prolonged through both systole and diastole of 

 the ventricle, between which there is a short but perceptible 

 pause, {h) Diminished impulse, appreciated by hand or eye, 

 and usually circumscribed as to extent of area of distribution, 

 is due to feebleness of the heart's action, and indicates disease 

 of the muscular structure ; in the horse this is usually soften- 

 ing from degenerative changes, or the diminution in force 

 may arise from debility, systemic or cardiac, and where there 

 is thinning of the walls of the heart's cavities ; also from the 

 presence of fluid in the pericardial sac. Further, it has been 

 found much diminished where the pericardium had contracted 

 adhesions to the lung-structures or the pleura of the right 

 side. 



3. Rhythm. — This may sufter disturbance in several ways. 

 (a) There may be irregularity as to character, force, or time ; 

 (6) The irregularity may have respect to the relation which 

 the impulse ought to bear to the ventricular systole. 



II. Auscultation of the Heart. 



A. Sounds of the Heart. — The sounds proper connected with 

 the heart are understood and, with some differences of opinion 

 I am aware, are accepted as the result of certain movements of 

 the heart or particular parts of its structure in connection 



