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PHYSIOLOGY FOR DENTAL STUDENTS. 



as the diastolic blood pressure. The average between these two 

 pressures is called the average or mean arterial blood pressure. 

 Since Hale's experiment better apparatus has been devised to 



Fig. 21. Apparatus for taking a tracing of the blood pressure. 



measure the blood pressure in animals under different conditions. 

 The standard method consists in placing a tube, called a cannula, 

 directly into a blood vessel. This is connected with a rubber 

 tube filled with an anti-clotting mixture (see Fig. 21) with one 

 arm of a U tube partly filled with mercury. When the blood ves- 

 sel is opened, the pressure of the blood will force the mercury 



