136 HUMAN PHYSIOLOGY CHAP. 



102. Sounds of the Heart. No machine can work 

 without noise. If you place your ear over the region 

 of the heart, two distinct sounds can be detected. 

 They occur in quick succession, followed by a short 

 pause. The first of these is a long, dull sound, caused, 

 we think, by the sudden sharp contraction of the ven- 

 tricles. The second is a sharp, short click caused by 

 the closing of the semilunar valves. These two sounds 

 are said to resemble the syllables " loob," "dup." 



To the physician these sounds indicate the condition 

 of the heart. He has an instrument, called the steth- 

 oscope, by means of which he can study the heart 

 sounds very accurately. Any change in their normal 

 pitch, force, or rhythm means a certain organic disturb- 

 ance or disease. 



103. The Pulse. When the ventricles contract 

 blood is forced out into the arteries, and their walls 

 dilate to make room for it. At every beat of the heart 



the arterial walls bulge out, 

 for they are as elastic as rub- 

 ber tubing. Then the walls 

 contract and push the blood 

 onward, causing a similar 

 wave elsewhere. These pul- 

 sations in the arteries, due to 

 FIG. 73. Showing how to find the contraction of their elastic 



the pulse (Scheinert). ,., . 



walls, constitute ULQ pulse. 



As a rule, the larger arteries lie near the bones and 

 quite removed from the surface of the body, but at cer- 

 tain places they come near the surface. Pulsations 



