COURSE OF CIRCULATION IN MAMMALS 155 



happening in the heart whilst one listens to its sounds. During the 

 first sound we have (1) contraction of the ventricles, closure of the 

 auric ulo- ventricular valves, and impulse of the apex against the 



I ' i 



jr^^l ^1 



; 



I 



'A^L 



Fia. (il. ELECTRO-CARDIOGRAM, CAROTID PCJLSE CURVE, AND HEART SOUNDS OP 



A DOG. (T. Lewis.) 



Tho, sounds arc recorded by a microphone fitted to a stethoscope connected with 

 a second string galvanometer. 



FIG. (52. ELECTRO-CARDIOGRAM AND ROUGH AORTIC MTJRMTT.I IN MAN. (T. Lewis.) 



chest; (2) rushing of the blood into the aortic and pulmonary artery, 

 and filling of the auricles. With the second sound we have closure 

 of the semilunar valves from the elastic recoil of the aorta and pul- 



