THE HEAKT-SOUNDS. 



71 



If the heart beats rapidly and feebly if the blood-pressure in the aorta and pulmonary 

 artery be low, the signs of closure of the pulmonary valves may be absent as in curve L 

 taken from a girl suffering from nervous palpitation and morbus Basedowii. 



In very rare cases of insufficiency of the mitral valve, it has been observed that at certain 

 times both ventricles contract simultaneously, as in a normal heart, but that this alternates 

 with a condition where the right ventricle alone seems to contract. Curve M is such a curve 

 obtained by Malbranc, who called this condition intermittent hemisystole. The first curve 

 (I.) is like a normal curve, during which the whole heart acted as usual. The curve II., how- 

 ever, is caused by the right side of the heart alone ; it wants the closure of the aortic valves, d, 

 and there was no pulse in the arteries. Owing to insufficiency of the tricuspid valve, the same 

 person had a venous pulse with every cardiac impulse, so that the arterial and venous pulses 

 first occurred together, and then the venous pulse alone occurred. In these cases the mitral 

 insufficiency leads to the right ventricle being overdistended, while the left is nearly empty, so 

 that the right side requires to contract more energetically than the left. It does not seem that 

 the right ventricle alone contracts in these cases, but rather that the action of the left side is 

 very feeble. 



53. THE HEART-SOUNDS. On listening over the region of the heart in a 

 healthy man, either with the ear applied directly to the chest-wall {Harvey), or by 

 means of a stethoscope (Laennec, 1819), we hear two characteristic sounds, the so- 

 called " heart-sounds." The two sounds are called first and second, and together 

 they correspond to a single cardiac cycle. These sounds are separated by silences. 

 [Fig. 50 shows the relation of the events occurring in the heart during a cardiac 

 cycle to the sounds and silences.] 



1. The first sound. 



2. The first or short silence. 



3. The second sound. 



4. The second or long silence. 



[Relative Duration. There is no absolute duration of each phase of a cardiac 

 cycle, but we may take the average duration calculated from the measurements of 

 Gibson, in a case of fissure of the sternum, to be as 

 follows : 



Auricular systole, 

 Ventricular systole, 

 Ventricular diastole, 



112 sec. 

 368 



578 



the first sound will last y 4 ^, the first silence r 



TO) 



and the long silence -^ of the 



Cardiac cycle, 1*058 sec. 



Suppose we divide the cycle into tenths ( Walshe), 

 then 



the second sound 

 entire period.] Fig. 50. 



The first sound [long or systolic] is twice as long Scheme of a cardiac cycle. The 

 as, somewhat duller, and one-third or one-fourth inner circle shows what events 

 deeper, than the second sound; it is less sharply occur in the heart, and the 

 defined at first, and is synchronous with the systole of ^ to th^e evenT 

 the ventricles. 



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 synchronous with 

 the closure of the semi-lunar valves. The sounds emitted during each cardiac cycle 

 have been compared to the pronunciation of the syllables lubb, dup. Or the result 

 may be expressed thus 



V V 



= 







11*11 



==* 



-# 



Bu 



-I 



'?- 



1/Ap. 



