VARIATIONS OF THE HEART-SOUNDS. 



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54. VARIATIONS OF THE HEART-SOUNDS. Increase of the first sound of both ventricles 

 indicates a more energetic contraction of the ventricles and a simultaneously greater and more 

 sudden tension of the auriculo-ventricular valves. Increase of the second sound is a sign of 

 increased tension in the interior of the corresponding large arteries. Hence increase of the 



The heart its several parts and great vessels in relation to the front of the thorax. The lungs 

 are collapsed to their normal extent, as after death, exposing the heart. The outlines of 

 the several parts of the heart are indicated by very fine dotted lines. The area of pro- 

 pagation of valvular murmurs is marked out by more visible dotted lines. A, the circle 

 of mitral murmur, corresponds to the left apex. The broad and somewhat diffused area, 

 roughly triangular, is the region of tricuspid murmurs, and corresponds generally with 

 the right ventricle, where it is least covered by lung. The letter C is in its centre. The 

 circumscribed circular area, D, is the part over which the pulmonic arterial murmurs 

 are commonly heard loudest. In many cases it is an inch, or even more, lower down, 

 corresponding to the conus arteriosus of the right ventricle, where it touches the wall of 

 the thorax. The internal organs and parts of organs are indicated by letters as follows : 

 r.au, right auricle, traced in fine dotting ; ao, arch of aorta, seen in the first intercostal 

 space, and traced in fine dotting on the sternum; v.i., the two innominate veins; r.v, 

 right ventricle ; l.v., left ventricle. 



second (pulmonary) sound indicates overfilling and excessive tension in the pulmonary circuit. 



A feeble action of the heart, as well as abnormal want of blood in the heart, causes weak 



heart-sounds, which is the case in degenerations of the heart-muscle. 



Irregularities in structure of the individual valves may cause the heart-sounds [to become 



