92 THE HEART-SOUNDS. 



stethoscope (Laennec, 1819), we hear two characteristic sounds, the 

 so-called " heart-sounds." Harvey was acquainted with these sounds, 

 but they have been more carefully studied by clinicians since the time 

 of Laennec. 



The first sound [long or systolic] is somewhat duller, longer, and 

 one-third or one-fourth deeper, than the second sound; it is less sharply 

 defined at first, and is isochronous, with the systole of the ventricles (TurnerJ. 

 The second sound [short or diastolic] is clearer, sharper, shorter, more 

 sudden, and is one-third to one-fourth higher ; it is sharply defined and 

 isochronous with the closure of the semi-lunar valves. There is a very 

 short interval between the first and second sounds, and between the 

 second and the next following first sound a distinctly longer interval. 

 This is the pause. 



[The sounds emitted during each cardiac cycle have been compared 

 to the pronunciation of the syllables lull, dup. We may express the 

 course of events with reference to the sounds, thus : lubb, dup, pause.] 

 Or the result may be expressed thus 



* *t * 



2?w tup. Bu - #p. 



The causes of the first sound are due to two conditions. As the 

 sound is heard in an excised heart in which the movements of the 

 valves are arrested, and also when the finger is introduced into the 

 auriculo-ventricular orifices so as to prevent the closure of the valves 

 (C. Ludwig and Dogiel), one of the chief factors lies in the " muscle- 

 sound " produced by the contracting muscular fibres of the ventricles 

 (Williams, 1835). 



This sound is supported and increased by the sound produced by the 

 tension and vibration of the auriculo-ventricular valves and their 

 chordaa tendinise, at the moment of the ventricular systole (Rouanet, 

 Kiwisch, Bayer, Giese). 



Wintrich, by means of proper resonators, has been able so to analyse 

 the first sound as to distinguish the clear, short, valvular part from the 

 deep, long, muscular sound. 



The muscle-sound produced by transversely-striped muscle does not occur with a 

 simple contraction, but only when several contractions are superposed to produce 

 tetanus (see Muscle). The ventricular contraction is only a simple contraction, 

 but it lasts considerably longer than the contraction of other muscles, and herein 

 lies the cause of the occurrence of the muscle-sound during the ventricular con- 

 traction. 



Defective Heart-Sounds. In certain conditions (typhus, fatty degeneration 

 of the heart) where the muscular substance of the heart is much weakened, the 



