8-i CLINICAL DIAGNOSTICS. 



[The first heart-sound (the systolic) is caused by the con- 

 tracting muscles of the organ and the closing of the auriculo-ven- 

 tricular valves. The second sound is produced by the closing of 

 the semilunar valves]. 



The first sound in our domestic animals is duller, deeper^ 

 more prolonged and usually louder than the second one. which 

 is short, not so deep, well defined (sharper), not so loud, and 

 at times slightly metallic. There is a great variation in the 

 sound produced by the heart in the dififerent animals, and even 

 in animals of the same species, the sounds being in one case 

 sharper (more metallic) and in another deeper and duller. 

 The thickness of the chest walls is also of influence, in ani- 

 mals with well muscled chests the sounds are seemingly more 

 muffled, duller. By pronouncing the syllables hib-duh one can. 

 mimic the sounds of the heart. 



I II I II 



lub dub lub dub 



Change in Heart-Sounds Due to Disease. 

 Both sounds are increased in: 



1. Hypertrophy of the heart, the valves remaining in- 

 tact, (idiopathic hypertrophy). 



2. Anemias. 



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 zveakened 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. 



