SPECIAL CLINICAL EXAMINATION. S7 



3. A thickening of the lung tissue around the heart, 

 producing a better conductor of sound. 



The second sound only is increased: 



When the arteries are greatly distended, not infrequently 

 the result of a congestion of the pulmonary circulation com- 

 bined with hypertrophy of the heart. 



Both sounds are weakened when the normal heart be- 

 comes enfeebled through disease of its parenchyma, or where 

 the hypertrophic organ is exhausted. 



Metallic tones occurring during systole are very com- 

 mon in anemic animals. In traumatic pericarditis of the 

 ox, the pericardium containing gas, a loud metallic tone is 

 heard at each systole when the heart-muscle is still vigorous. 

 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 |— ~| — — | 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 -| — ~| , 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. 



1. 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- 



