278 



addition of any substance (though increasing the specific gravity), 

 whether in solution, or merely suspended in the water, heightens it ; 

 that particles in suspension, indeed, heighten it more than solutions. 



The fact of different fluids raising the pitch in variable degrees, 

 excludes the possibility of the rise being due to the glass, or any 

 other material used, unless the fluid varying in weight altered the 

 pitch, by affecting the tension of the diaphragm ; but the fact of the 

 alteration in pitch bearing no relation to the specific gravity of the 

 fluid excludes this source of error. 



The following experiments were devised to test the influence of 

 running water on the pitch. 



Into an india-rubber tube, 1 3 inches long, and f ths of an inch 

 diameter, a funnel was inserted ; immediately below this a small 

 opening was made, just large enough to admit the end of the fork. 

 Water was kept constantly running through this, and the stethoscope 

 (covered with a diaphragm) applied to different parts of the tube ; 

 by this method the pitch was found to be most appreciably raised the 

 further from the fork the stethoscope was applied to the tube. The 

 elevation of pitch was easily recognized at a distance of 2^ inches 

 (the length of the pulmonary artery and adjoining part of the aorta). 



The stethoscope having been unfortunately left behind, Dr. Wylde 

 could only apply the ear directly to the tube, and therefore could not 

 speak so decidedly as he did concerning the other experiments, but 

 he was of opinion that the pitch was raised as stated above. 



It was next attempted to be ascertained whether the mere motion 

 of the water increased or diminished the rise of the pitch. It ap- 

 peared that the pitch was very slightly raised by the mere motion 

 of the fluid, the same point of the tube being listened to. The 

 difference in intensity was most marked. 



The chief object of these experiments being to ascertain the in- 

 fluence of the different constituents of the human body on the pitch 

 of cardiac and other murmurs, and in order that the experiments 

 might, as closely as possible, simulate the actual phenomena in the 

 body, an aorta was tied to the mouth of a tap, and an artificial 

 murmur produced by causing a constriction of the vessel by a piece 

 of twine tied round it. The pitch of the murmur so produced was 

 decidedly raised the further it was heard along the vessel from the 

 point where the sound was generated. 



