LABORATORY MANUAL OF PHYSIOLOGY. 



pressure is read off on the manometer scale in millimetres of mer- 

 cury. 



If now the pressure is released until the widest oscillations of 

 the mercury meniscus are just secured and a reading is then taken, 

 the diastolic pressure is shown. This may be more accurately de- 

 termined by palpating the pulse and inflating the tube until the 

 first perceptible diminution of the pulse occurs. To reduce error 

 as much as possible, the arm tube and cuff should be at least 

 twelve centimetres in width. 



With some such instrument as that described above, make a 

 number of determinations of both systolic and diastolic pressure 

 of one individual. Repeat the observations on other individuals of 

 the class. If there are other instruments at hand for this same 

 purpose, make observations with several different instruments on 

 the same individual. 



Make an observation on a normal individual. Allow the subject 

 to take several whiffs of amyl nitrite and observe the blood pressure. 



120] 



