126 THE VASCULAR SYSTEM 



seriously into play we should not expect this correspondence, for 

 it is unlikely that the arteries on the two sides would be equally 

 degenerated and rigid. It is also unlikely that they would be 

 equally contracted, because an artery exposed to lessened blood 

 pressure dilates, while to increased blood pressure it contracts. 

 We should expect, therefore, the artery in the upraised arm to 

 be less contracted than the other. In one case of aneurism they 

 were quite unable to make these tests owing to the greatly varying 

 inequality of the heart strokes. Tested on the thigh of dogs both 

 the armlet and the writer's pocket sphygmometer gives the same 

 readings as the opposite femoral artery taken directly with cannula 

 and manometer. 



The conclusion the writer has come to, then, is that the method 

 is exact, when carried out with either the armlet or the large 

 enclosed bag of his pocket sphygmometer, and that these are the 

 simplest and best methods of testing the systolic arterial pressure 

 in man. The first act of obliteration must relax the artery and 

 make subsequent readings exact. 



It has been suggested that during obliteration of such a large 

 artery as the brachial, the general arterial pressure may rise, but 

 no error arises thus, if two or three consecutive readings be taken. 

 The readings should be taken when the excitement and novelty of 

 the operation has passed off, as emotional excitement raises the 

 pressure considerably. Thus the writer's pressure in the morning 

 is 110 to 115 in the holidays, and 140 when teaching and working 

 in the laboratory. He has observed the pressure to rise 10 mm. Hg 

 on addressing a question to the subject. There is no advantage 

 gained by reading the pressures nearer than within 5 mm. Hg, or 

 in the use of complicated instruments for recording the maximal 

 oscillations, such as that of Erlanger. 



The average systolic pressure of the resting man according to 

 a number of observations taken by H. J. Starling is 



15 to 40 years .... 119 



41 to 60 142 



61 and over .... 165 



but some robust old men, he says, have pressures no higher than 

 those of the young. 



The writer has found the pressure to be as low as 80 mm. Hg 

 in children ; to be 80 to 110 in young adults ; and to be no higher 



