86 CLINICAL DIAGNOSTICS. 



The Auscultation of the Heart. 



Method. The auscultation of the heart may be practiced by 

 placing the right ear just behind the left elbow, the leg being 

 drawn forward. Small animals may be laid upon the table and 

 the stethoscope used. 



Physiology. In the cardiac region and in the neighborhood of 

 the same, we hear at each action of the heart two tones. One 

 of these tones appears at the moment the organ contracts (systole), 

 and the second tone, which quickly follows the first, at the dila- 

 tion of the organ (diastole). The second tone follows so closely 

 the first one that it is difficult to differentiate between them, ex- 

 cept in animals which carry a pulse below 60. In animals which 

 have a rapid pulse it may be necessary to compare the pulse at a 

 peripheral artery with the heart's beat. 



The origin of the heart-tones is still subject to dispute, the 

 authorities not agreeing. 



[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 different 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 lub-dub 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. 



