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ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 



spring which must be calibrated from time to time by comparing its 

 movements with those of a column of mercury under equal degrees of 

 pressure. Since the mercury manometer usually consists of one vertical 

 limb leading away from a central reservoir, the pressure may be read 

 off directly without correction. Some instruments, however, contain a 

 U-shaped tube, in which case the pressure, as read off from the ascend- 

 ing limb, must be multiplied by 2. 



FIG. 82. SPHYGMOMANOMETER, RECENT TYPE. (Manufactured byW.A. Baum Co., N. F.) 



The subject should be comfortably seated in a chair with his right 

 forearm resting upon a table. Adjust the armpiece of the sphyg- 

 momanometer (modification of the Riva-Rocci instrument) to the arm 

 of the subject. Be sure that the lower edge of the cuff does not encroach 

 upon the elbow and is not applied too loosely. Two methods may be 

 followed in determining the blood-pressure, namely, palpation and 

 auscultation. 



(a) Palpation. Having adjusted the armpiece accurately, locate the 



