192 SOUNDS WITHIN ARTERIES. 



97. Sounds or Bruits within Arteries. 



These murmurs, sounds, or bruits occur either spontaneously, or are produced 

 by the application of external pressure, whereby the lumen of the vessel is 

 diminished. In four-fifths of all healthy men two sounds corresponding in 

 duration and other characters to the two heart-soundsare heard in the carotid 

 (Conrad, Weil). Sometimes only the second heart-sound is distinguishable, as its 

 place of origin is near to the carotid. They are not true arterial sounds, but are 

 simply "propagated heart-sounds." 



Arterial Sounds or murmurs are readily produced by pressing upon 

 a strong artery e.g., the crural in the inguinal region, so as to leave 

 only a narrow passage for the blood ("Stenosal murmur"). A fine 

 blood-stream passes with great rapidity and force through this narrow 

 part, into a wider portion of the artery lying behind the point of com- 

 pression. Thus arises the " pressure-stream " (P. Niemeyer), or the 

 "fluid vein" (" Veine fluide" of Chauveau.) The particles of the fluid 

 are thrown into rapid oscillation, and undergo vibratory movements, 

 and by their movement produce the sound within the peripheral 

 dilated portion of the tube. A sound is produced in the fluid by 

 pressure (Corrigan, Heynsius). The sounds are not caused by vibra- 

 tions of the vascular wall, as supposed by Bouillaud. 



A murmur of this sort is the " sub -clavicular murmur" (Roser), 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). 



Arterial murmurs are favoured by (1) Sufficient delicacy and 

 elasticity of the arterial walls (Th. Weber). (2) Diminished peri- 

 pheral resistance e.g., an easy outflow of the fluid at the end of the 

 stream (Kiwisch). (3) Accelerated current in the vascular system 

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

 narrow and wide portions of the tube (Marey). (5) Large calibre of 

 the arteries. 



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, within 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, (c.) A murmur corresponding to each pulse-beat is heard, especially where 

 two or more large arteries lie together ; hence, during pregnancy, we hear the uterine 

 murmur, or placenlal 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 (Fisher, 1833). A 

 murmur due to the systole of the heart is often heard in the carotid (Jurasz). In such 



