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CHAPTER IV. 



THE APPLIED PHYSIOLOGY OF 

 BLOOD-PRESSURE. 



Apparatus for measuring arterial, venous, and capillary pressure 

 in man Factors controlling the blood-pressure The influence 

 of gravity The influence of the internal secretion of the supra- 

 renal glands Surgical shock : its nature, prevention, and treat- 

 ment The intracranial circulation Blood-pressure after head 

 injuries The pulmonary circulation The internal administration 

 of haemostatics. 



IT has become a truism that when feeling the 

 pulse it is of more importance to observe the 

 " tension," or blood-pressure, than to count the rate. 

 But only within the last few years has it been 

 recognized how inadequately even the skilled finger 

 can judge of the blood - pressure, because of the 

 complicating factor of the variable rigidity of the 

 arterial wall. In an arteriosclerotic vessel the 

 tension will be over-estimated. 



Two well-known apparatus have therefore been 

 introduced to clinical service. The first to be widely 

 used in England was Hill and Barnard's sphygmo- 

 meter, and later came some form of the Riva-Rocci 

 instrument. Both may be used to measure either 

 the systolic or the diastolic pressure. They have in 

 common a hollow rubber armlet capable of inflation 

 with air, and covered by a leather or leaden shield 

 to be strapped round the arm ; each is to be inflated 

 by an air-pump with a leaking valve, so that the 



