FREQUENCY OF THE HEART'S ACTION 41 



closure. It is relatively high in pitch on account of the shorter length 

 of the free borders of the valves. It is heard at its maximum of inten- 

 sity over the semilunar valves on either side of the upper part of the 

 sternum and~is conducted upward along the great vessels. 



Placing the stethoscope over the apex of the heart and a little to the 

 left, it is possible to distinguish the sound produced by closure of the 

 mitral valve ; and with the stethoscope just below the ensiform cartilage, 

 the sound produced by the tricuspid valve may be distinguished. In 

 the same way, if the stethoscope is placed a little to the right of the 

 sternum, near the aortic valves, the sound produced by these valves may 

 be distinguished, while to the left of the sternum, near the pulmonic 

 valves, the sound produced by these valves becomes more distinct. 



A cardiac cycle with reference to the heart-sounds is somewhat 

 different from the cycle described with reference to the contractions of 

 the heart. The cycle, as it relates to the sounds, is as follows : during 

 four-eighths of the cycle, the first sound is heard ; this is followed im- 

 mediately by the second sound, which occupies three-eighths of the cycle. 

 One-eighth of the cycle is silence. 



It is of great importance to connect the heart-sounds with the blood- 

 currents. During the first sound, the auriculo-ventricular valves are 

 closed, the semilunar valves are open, and, as a consequence, the blood 

 is flowing from the left ventricle into the aorta and from the right 

 ventricle into the pulmonary artery. During the second sound, the 

 blood is flowing into the auricles, a small quantity is passing into the 

 ventricles, the semilunar valves are closed and the auriculo-ventricular 

 valves are open. 



Frequency of the Heart's Action. The number of pulsations of 

 the heart is not far from 70 per minute in an adult male and is be- 

 tween 70 and 80 in the female. There are cases, however, in which 

 the pulse is normally much slower or more frequent than this, a fact 

 that must be remembered when examining the pulse in. disease. It 

 is said that the pulse of Napoleon I was only 40 per minute, and 

 that the pulse of Sir William Congreve was never less than 128 

 per minute in health. It is not unfrequent to find a normal pulse of 

 a hundred or more a minute ; but in the cases reported in which the 

 pulse has been found to be 40 or less, it is possible that each alter- 

 nate beat of the heart was so feeble as to produce no perceptible 

 arterial pulsation. In such instances, the fact may be ascertained 

 by listening to the heart while the finger is placed upon the artery. 



In both the male and the female, observers have constantly found 

 a difference in the rapidity of the heart's action at different periods of 

 life. The pulsations of the heart in the foetus are about 140 per minute. 



