THE HEART-SOUNDS. 



Ill 



The sound is augmented and reinforced by the tension and vibra- 

 tions of the auriculo-ventricular valves and their tendinous bands at 

 the instant of ventricular contraction. 



Wintrich, in 1873, succeeded by the use of suitable resonators in dis- 

 tinguishing one sound from the other; the clearer and shorter valvular 

 sound from the deeper and more protracted muscular tone. 



FIG. 34. Topography of the Thorax and of the Thoracic Viscera: a. d., right auricle; o. s., left auricle; v. d., 

 right ventricle; I, left ventricle with I t apex of the heart; A, aorta; II, pulmonary artery; C, superior vena 

 cava; L L, boundaries of the lungs; P P, boundaries of the parietal pleura (v. Luschka and v. Dusch). 



Under pathological conditions, such as typhoid fever and fatty heart, in which 

 the heart-muscle is greatly enfeebled, the first sound of the heart may be inaudible. 

 In the presence of insufficiency of the aortic valves, when, owing to the regurgita- 

 tion of the blood from the aorta into the ventricle, the mitral valve is made tense 

 gradually and before the ventricular systole begins, the first sound of the heart 

 is also not infrequently absent. Both of these pathological instances prove that 

 the cooperation of muscle-tone and valve-tone is required for the production of 

 the first sound of the heart and that when one of these elements is lost the heart- 

 sound may become inaudible. It should further be mentioned that the vibra- 

 tions of the semilunar valves before or during their closure and the vibrations 

 of the fluid elements of the blood itself have been adduced as contributory factors 

 in the explanation of the first sound of the heart. 



