110 THE HEART-SOUNDS. 



may be entirely obliterated, as in curve L taken from a girl with exophthalmic 

 goiter who suffered from nervous palpitation of the heart. 



In rare cases of mitral insufficiency a condition in which the right ventricle 

 is greatly overfilled with blood, while the left contains but little, so that the right 

 has to work harder to empty itself than does the left a peculiar action of the 

 heart has been observed, both ventricles appearing at times to contract together 

 and then again the right ventricle alone (Fig. M after Malbranc) . Curve I , which 

 appears in every respect like a normal apex-beat curve, was taken when the entire 

 heart was active; there was present an arterial pulse corresponding to this apex- 

 beat. Curve II, on the other hand, appears to have been recorded by the right 

 heart alone, and it accordingly lacks the closure of the aortic valves (d) ; nor 

 was there an arterial pulse corresponding to this contraction. 



With respect to the cases just considered Landois expressed the opinion as 

 early as 1879 that the phenomenon could not be explained on the mere supposition 

 that the right ventricle alone is active during the phases in question, without any 

 parallel action on the part of the left. He regarded such a condition as impossible, 

 if for no other reason because of the common arrangement of the muscles in the 

 two ventricles and their equally common innervation. The period of apparent 

 rest of the left ventricle is probably no more than a period of exceedingly feeble 

 action, not strong enough to record itself in the apex-beat curve by the closure 

 of the aortic valves and by a pulse in the arteries. This supposition has in fact 

 been confirmed by Riegel and Lachmann, Eger, Eichhorst, Stern, H. E. Hering, 

 and others. 



THE HEART-SOUNDS. 



On listening over the region of the heart, either directly with the 

 ear applied to the thorax, or with the aid of the stethoscope, or in ani- 

 mals to the exposed heart, two sounds are audible that really do not 

 deserve the name of tones, but which in contradistinction from pathologi- 

 cal heart-murmurs are designated heart-sounds. As they possess a cer- 

 tain tonal color, it has been possible to determine their musical pitch. 



The first sound of the heart is somewhat duller, longer, and lower 

 in pitch by a third or fourth, fluctuating between d sharp and g, not 

 clearly denned, especially at the beginning, and synchronous with the 

 ventricular systole. The second sound of the heart is clearer, more 

 valvular, shorter, and therefore more distinctly marked, varying between 

 f sharp and b flat, clearly defined, and synchronous with the closure of 

 the semilunar valves. The first sound is separated from the second 

 by a short interval, and the second sound from the succeeding first 

 sound by a longer interval. In musical parlance the first sound appears 

 as a rising beat to the second, which is then followed by the pause. 

 The vibration-values and the rhythm may accordingly be expressed 

 as follows : 



Y 



Bu - tup (lub-dup) Bu'- tup (lub-dup) 



The first sound is caused by two factors. As it is heard, though 

 faintly, in excised hearts in which the auriculo- ventricular valves are 

 prevented from being stretched and relaxed, and as it is heard also 

 when the movement and closure of the valves are prevented by means 

 of a finger introduced into the auriculo- ventricular orifice, the principal 

 cause of the sound is to be sought in the muscular murmur, produced by 

 the contracting muscular fibers of the ventricles. 



