122 THE VASCULAK SYSTEM 



flaccid, and so closely confined by a rigid covering that the pressure 

 cannot be spent in distending its wall rather than in compressing the tis- 

 sues. The armlet satisfies all the requirements if it be large enough 

 (20 cm. broad), and be bound round so as to closely fit the arm. 



The writer has introduced a sphygmometer which gives the 

 same readings as the armlet, and can be carried conveniently in 

 the pocket. It consists of a flaccid rubber ball enclosed in a 

 silk cover, and a gauge which can be carried in a case like that 

 of a clinical thermometer. The gauge is formed of a glass tube 

 closed at one end and having a hole in the side near the open 

 end. If the open end be placed in water, the water meniscus 

 rises as far as the hole in the side. 1 The rubber tube of the 

 bag is then slipped over the gauge until this hole is covered. 

 On now pressing the bag the meniscus rises up the gauge and 

 compresses the air before it. The air acts as a spring, and the 

 stem of the gauge is calibrated in mm. Hg by testing it against 

 a Hg manometer. To use the instrument properly the bag must 

 be only partially full of air, and must be entirely covered with 

 the fingers and palm of the hand, and then pressed upon the 

 radial artery, the thumb of the hand exerting a counter pressure 

 against the back of the wrist. 2 The arm must be held at the 

 same level as the patient's heart apex to eliminate the influence 

 of gravity, and the radial artery must be felt with the fingers of 

 the other hand, the second finger being employed to prevent the 

 pulse regurgitating from the ulnar, while the first finger deter- 

 mines when the radial pulse disappears. The operator, when 

 setting the index, holds the gauge by the solid glass end, so that his 

 fingers may not heat the air within. The gauge when taken out of 

 the pocket must be cooled to room temperature before it is used. 



The instrument may be used, but not very easily, to obtain 

 the maximal pulsation. To effect this as little air as possible 

 must be used in the bag, and the bag must be closely confined to 

 the hand. There is some debate as to when maximal pulsation 

 occurs. According to Roy and Adami, and to Howell and Brush, it 

 occurs when the pressure just exceeds the minimal or diastolic 

 pressure as recorded by a Hiirthle manometer connected directly 

 with the artery. Hill and Barnard, however, found when the armlet 



1 If water gets into the side hole it must be blown out, or else the meniscus will 

 not rise. 



* The fingers grip the junction of tube and gauge and support the latter. 



