SPECIAL CLINICAL EXAMINATION. 85 



Sometimes the sound can be plainly heard the distance of 

 several paces from the affected animal. 



This is due to the accumulation of gas in the pericardium 

 acting as a resonant mechanism which augments the sound. 



The first tone is dull in heart's weakness and in myocar- 

 ditis, especially noticeable in acute infectious diseases. 



A splitting W^—^^l — -—I or doubling |— --| — — | of the 

 heart sounds, the condition of the circulatory apparatus being 

 otherwise normal, is of no significance. Commonly the first 

 sound is preceded by a short tone -| 1 , which is pro- 

 duced by the contracting of an unusually well developed 

 auricle. 



Heart bruits. Heart bruits are abnormal 

 sounds and are therefore pathological. They are caused 

 by the sound producing parts of the organ vibrating for too 

 long a time. Endocardial bruits and pericardial bruits are 

 distinguished. 



a. Endocardial bruits (noises) come from 

 within the heart and are closely connected with the heart 

 sounds. We can distinguish, therefore, systolic bruits and 

 diastolic bruits, depending upon whether they occur at the 

 first or second sound. If the bruits are produced by anatomi- 

 cal changes of the heart itself, they are called organic, other- 

 wise inorganic. 



a. The organic or endocardial heart bruits are caused 

 either by a narrowing (stenosis) of the auriculo-ventri- 

 cular or arterial openings or by alterations on the valves pre- 

 venting them from closing properly (insufficiency). 

 They form most valuable symptoms in the diagnosis of heart 

 diseases. 



Instenosisthe bruitoccursatthemoment 

 the blood passes the contracted orifice, the 

 walls of which are set in vibration. If the stenosis involves 

 the auriculo-ventricular opening the bruit occurs at diastole, if 

 in the arterial openings, at systole. 



