268 The Symballophone 



scribed as (i) those which are propagated on the pulse wave and leave the 

 heart through the aortic or pulmonary valve, and (2) those which are propa- 

 gated through the tricuspid or mitral valve into the auricles. The former 

 travel widely on the pulse wave along the course of the aorta or pulmonary 

 artery and frequently are accompanied by a palpable thrill because of the 

 proximity of these vessels to the surface of the chest. Those propagated along 

 the pulmonary artery are not transmitted widely, in no case beyond the chest. 

 Systolic murmurs associated with backflow through the tricuspid valve are 

 heard over the lower portion of the sternum which is nearest to the right 

 auricle. The systolic murmur of mitral insufficiency is heard best at the apex 



Direction o"f -flow. 



I Jiito^ 



ilppv"^"^""' 



Murmurs Produced by Faults in Strf.amlimng 

 Murmurs travel both ways from point of constriction, but 

 for a greater distance in the direction the liquid is flowing. 



Fig. 8. A simple elastic tube such as a garden hose through \\hich liquid is flo\ving may be 

 used to illustrate the effects of compression that cause faults in streamlining. Obstructions in 

 the heart at the orifices of the valves, or variations in the size of the lumina of vessels, cause 

 faults in streamlining which produce vibrations that may be heard as murmurs. 



and is transmitted toward the left axilla and left subscapular region which is 

 nearest to the left ventricle and auricle. The intense systolic pressure in the 

 left ventricle drives the blood backward through the aperture in the defective 

 mitral valve with such force that the sounds produced are louder and more 

 widely propagated. The proximity of the contracted left ventricular muscle 

 in systole to the wall of the chest permits more direct propagation of the 

 vibrations which produce the murmur. The vibrations travel in both direc- 

 tions from the point of origin but for a greater distance in the direction of the 

 blood flow, as will be described. 



If a simple compressible elastic tube, for example, a garden hose, through 

 which liquid is flowing (figs. 8 and g) is compressed, vibrations are produced in 

 the walls of the tube and eddies form in the liquid. If the tube is palpated in 

 front of and beyond the point of constriction, the vibrations are felt as thrills. 

 AV^ith the stethoscope, sounds are heard which may be designated as murmurs. 

 These sounds may be heard for some distance in both directions from the 

 point of compression but always for a greater distance in the direction of the 

 flow of the liquid. Let us now apply these observations to the heart and blood 

 vessels. Two good clinical examples of this kind are aortic stenosis and pul- 

 monary stenosis in which the diseased valves provide the partial obstructions, 



