SPONTANEOUS MURMURS. 141 



of the fluid are thrown into rapid oscillation, and undergo vibratory movements, and 

 by their movements produce the sound within the peripheral dilated portion of the 

 tube. A sound is produced in the fluid by pressure (Corrigan). The sounds are 

 not caused by vibrations of the vascular wall, as supposed by Bouillaud. 



A murmur of this sort is the "sub-clavicular murmur" (Eoser), occasionally heard during 

 systole in the subclavian artery ; it occurs when the two layers of the pleura adhere to the apex 

 of the lung (especially in tubercular diseases of the lungs), whereby the subclavian artery 

 undergoes a local constriction due to its being made tense and slightly curved (Friedreich). 

 This result is indicated in a diminution or absence of the pulse -wave in the radial artery ( Weil). 



It is obvious that arterial murmurs will occur in the human body : (a) When, owing to 

 pathological conditions, the arterial tube is dilated at one part, into which the blood-current is 

 forcibly poured from the normal narrow tube. Dilatations of this sort are called aneurisms, 

 in which murmurs are generally audible. (b) When pressure is exerted upon an artery, 

 e.g., by the pressure of the greatly enlarged arteries during pregnancy, or by a large tumour 

 pressing upon a large artery. 



Spontaneous Murmurs. In cases where no source of external pressure is discoverable, and 

 when 110 aneurism is present, the spontaneously occurring sounds are favoured, when at the 

 moment of arterial rest (cardiac systole) the arterial walls are distended to the slightest extent, 

 and when during the movement of the pulse (cardiac diastole) the tension is most rapid ( Traubc, 

 Weil), i.e., when the low systolic minimum tension of the arterial wall passes rapidly into the 

 high maximum tension. This is especially the case in insufficiency of the aortic valves, in 

 which case the sounds in the arteries are audible over a wide area. If the minimum tension of 

 the arterial wall is relatively great, even during diastole, the sounds in the arteries are greatly 

 diminished. 



Arterial murmurs are favoured by (1) Sufficient delicacy and elasticity of the 

 arterial walls. (2) Diminished peripheral resistance, e.g., an easy outflow of the 

 fluid at the end of the stream. (3) Accelerated current in the vascular system 

 generally. (4) A considerable difference of the pressure in the narrow and wide 

 portions of the tube. (5) Large calibre of the arteries. 



In normal pulsating arteries, sounds may be heard especially at an acute bend of the artery. 

 Murmurs of this sort are loudest where several large arteries lie together; hence, during 

 pregnancy, we hear the uterine murmur, or placental bruit, or souffle in the greatly dilated 

 uterine arteries. It is much less distinct in the umbilical arteries of the cord (umbilical 

 murmurs). Similar sounds are heard through the thin walls of the head of infants, and a 

 murmur is sometimes heard in the enlarged spleen in ague (Maissurianz). 



Auscultation of the Normal Pulse. On auscultating the radial artery under favourable cir- 

 cumstances, and especially in old thin persons with wide arteries and dicrotic pulse, one may 

 hear two sounds corresponding to the primary and dicrotic waves. 



In insufficiency of the aortic valves, characteristic sounds may be heard in the crural artery. 

 If pressure be exerted upon the artery, a double blowing murmur is heard ; the first one is due 

 to a large mass of blood being propelled into the artery synchronously with the heart-beat, the 

 second to the fact that a large quantity of blood flows back into the heart during diastole. If 

 no pressure be exercised two sounds are heard, and these seem to be due to a wave propagated 

 into the arteries by the auricles and ventricles respectively compare 73, fig. 86, III. In 

 atheroma a double sound may sometimes be heard ( 73, 2). 



98. VENOUS MURMURS. I. Bruit de Diable. This sound is heard above 

 the clavicles in the furrow between the two heads of the sterno-mastoid, most 

 frequently on the right side, and in 40 per cent, of all persons examined. It is 

 either a continuous or a rhythmical murmur, occurring during the diastole of the 

 heart or during inspiration ; it has a whistling or rushing character, or even a 

 musical quality, and arises within the bulb of the common jugular vein. When 

 this sound is heard without pressure being exerted by the stethoscope, it is a 

 pathological phenomenon. If, however, pressure be exerted, and if, at the same 

 time, the person examined turn his head to the opposite side, a similar sound is 

 heard in nearly all cases. The pathological bruit de diable occurs especially in 

 anaemic persons, in lead poisoning, in syphilitic and scrofulous persons, sometimes 

 in young persons, and less frequently in elderly people. Sometimes a thrill of the 

 vascular wall may be felt. 



Causes. It is due to the vibration of the blood flowing in from the relatively 

 narrow part of the common jugular vein into the wide bulbous portion of the 



