94 



SPECIAL PHYSIOLOGY 



of the mercury manometer in measuring the pressure in a pneumatic 

 arm-girdle so adjusted as to suppress or to modify the pulse. An 

 accurate determination of blood pressure is occasionally of very great 

 importance, and it goes without saying that methods used on the 

 lower animals are not applicable in the case of man because they 

 involve the opening of an artery. 



The only appliance needed is the sphygmomanometer (Fig. 53) 

 and the only preparation is for a member of the class to remove 

 clothing from one arm. 



Observations. (1) Let the subject lie upon his back on the 

 table in an easy and comfortable position, and absolutely relaxed 

 and quiet for five minutes. During this period the girdle may be 



FIG. 53 



The sphygmomanometer : O, arm-girdle with inflatable rubber tube (() within and sole-leather 

 belt (6) without ; P, pressure bulbs ; .m, mercury manometer. 



fastened about the right arm. While one observer is counting the 

 pulse at the left wrist, another may feel the right pulse. A third 

 observer may watch the manometer while he gradually pumps air 

 into the girdle until the pulse is shut off at the wrist. Read the 

 manometer, relax the girdle pressure until the pulse reappears. 

 Read the manometer. The mean between the two readings as thus 

 made is taken to represent the pulse pressure. Record the pulse 

 rate as counted on the left pulse. Record the pulse pressure as 

 determined by the sphygmomanometer. 



(2) Let the subject lie on his right side. Take observations as 

 outlined above and record pulse rate and pulse pressure. 



