THE GIKCULATION OF THE BLOOD 



527 



bour and the manometer into the same vertical 

 line against a smoked drum. Let the drum re- 

 volve at a fast speed. 



Place the button of the receiving tambour on 

 the aorta. It will record the aortic pulse and 

 the membrane 

 manometer will 

 record the intra- 

 ventricular pres- 

 sure. Let the 

 ventricle pump 

 with the usual 

 force and fre- 

 quency. When 

 the two curves 



Fig. 70. The sphygmograph. 



have been writ- 

 ten stop the 



clockwork and turn back the drum until the 

 point of the lever recording the ventricular pres- 

 sure lies at the exact beginning of the upstroke 

 in the aortic pulse curve. Cause each lever to 

 write an ordinate on the stationary drum. These 

 ordinates will indicate synchronous points and 

 will mark the beginning of the "outflow" period. 



The Sphygmograph Tambour. 1 This small and 

 very sensitive tambour (Fig. 71) is mounted upon a 



1 First Catalogue of Harvard Physiological Apparatus, 1901, 

 p. 47. 



