Physical diagnosis, including diseases of the thoracic and abdominal organs : a manual for students and physicians .. . spring holding the ear piecesin place should not be too stiff, and where the instru-ment has to be used for long periods of time each day aform of stethoscope should be used in which the pressureof the spring can be regulated. The examination should be made methodically, andthose portions of the heart should be first examinedwhere the cardiac sounds are most distinct, both as tointensity and their relation to the ventricular systole. Normal Cardiac Sounds.—Two sounds are prod
Physical diagnosis, including diseases of the thoracic and abdominal organs : a manual for students and physicians .. . spring holding the ear piecesin place should not be too stiff, and where the instru-ment has to be used for long periods of time each day aform of stethoscope should be used in which the pressureof the spring can be regulated. The examination should be made methodically, andthose portions of the heart should be first examinedwhere the cardiac sounds are most distinct, both as tointensity and their relation to the ventricular systole. Normal Cardiac Sounds.—Two sounds are produced bycardiac action, each having a definite relation to thephase of cardiac cycle and differing in time, character,position of maximum intensity and area of diffusion. AUSCULTATION. 287 First Sound.—The first sound of the heart corre-sponds to the ventricular systole, closure of the mitraland tricuspid valves and opening of the aortic and pul-monary valves, with forcing of the blood stream fromthe right and left ventricular cavities into the pul-monary artery and aorta. The first sound of the heart Fig. Area of crunching first sound. is a prolonged, low-pitched, dull sound, which has someresemblance to the sound made in the pronunciation ofthe syllable lubb. The cause of the first sound of the heart is still amatter of dispute. Numerous theories have been ad- 288 THE CIRCULATORY SYSTEM. vanced, but no one of them has been universally consensus of opinion is that the first sound of theheart is composed of two elements: (a) The muscularelement, due to the contraction of the cardiac muscleand its impact on the chest wall, giving the prolonged,dull, low-pitched quality, (b) The valve element, dueto the closure of the mitral and tricuspid valves andstretching of the chorda? tendinese and papillary muscle,causes the short, sharp and high-pitched quality. Aswill be explained under Modifications of .NormalSounds, the first sound will vary according as one or theo
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