282 SIXTH REPORT — 1836. 



ventricle by the hand, and relaxation being renewed, two sounds 

 were heard, both prolonged, the second having lost the abrupt- 

 ness by which it had been previously characterized. 



Experiment 3. — The experiment now to be described was 

 first made by M. Rouanet, and is detailed by M. Bouilleaud, in 

 his work on the diseases of the heart. It consists in attaching 

 hy one end, a glass tube a few inches in length, and about an 

 inch wide, to a bladder holding water, and by the other to the 

 aorta, close beneath the semilunar valves, but so as not to inter- 

 fere with their movements ; the muscular substance of the heart 

 having been previously removed. Another glass tube, some 

 feet long, and of equal diameter with the former, is tied into 

 the aorta at a distance of two or three inches above the semilu- 

 nar valves. The bladder is compressed by the hand so as to 

 raise the water in the tube to a considerable height; and the 

 hand being suddenly relaxed, the column of water in the longer 

 tube, deprived of support, descends until it is arrested by the 

 closing of the semilunar valves. At this instant, if the ear have 

 been applied to the lower part of the longer tube, an abrupt 

 sound is heard, resembling the second sound of the heart. If 

 the semilunar valves be now removed, and the experiment with 

 this alteration, be repeated, the sound, which is heard to ac- 

 company the relaxation of the heart, is no longer abrupt, but 

 prolonged. 



The conclusions which the Committee have drawn from these 

 experiments, as to the causes of the ordinary sounds of the heart, 

 are similar to those detailed in their former Report, to which 

 they beg leave to refer. 



It appears to the Committee that many writers upon the sounds 

 of the heart have not sufficiently distinguished the characters of 

 those sounds, the prolongation of the first, and the abruptness 

 of the second; and the term " tic-tac" which has been em- 

 ployed to express their rythm, is likely to mislead inaccurate 

 observers by representing the sounds as of equal length. 



The first sound, of a homogeneous character, beginning and 

 ending with the ventricular systole, which is a prolonged action, 

 coincides with it in duration ; and the observation of this fact 

 has enabled the Committee to exclude fr(»m the causes of the 

 first sound, all those which are of a momentary nature, as the 

 closing of valves, and those possessing the character of im- 

 pulse. 



In concludhig their second Report, the Committee wishtostate 

 their opinion that the motions and sounds of the heart have 

 been now, by themselves and others, investigated nearly as far 



