508 



CIRCULATION OF BLOOD AND LYMPH. 



within the vein. A convenient modification of this apparatus, which has 

 been described by Hooker,* is shown in Fig. 207. A small glass chamber is 

 fastened on the hand over a vein by means of a film of collodion solution. 

 The interior of the chamber is connected by rubber tubing with a water 

 manometer and a pressure bulb. By means of the latter the air pressure on 

 the vein may be raised until the vein is just obliterated and the pressure used 

 is indicated on the manometer in centimeters of water. 



With instruments of this kind the degree of pressure neces- 

 sary to obliterate a given vein in the arm, hand, or foot can 



Fig. 207. Hooker's venous pressure apparatus. A glass capsule, A, is fastened to the skin 

 over a vein by means of a solution of collodion. This capsule is connected by rubber tubing 

 with a pressure^bulb, C, and a water manometer, M. By means of the bulb the pressure is 

 raised in A until the vein is obliterated. The pressure at which this occurs is shown by the 

 level of the liquid in the manometer. This pressure, expressed in centimeters of water, is cor- 

 rected by subtracting the distance between the vein and the costal angle, as indicated on the 

 metal rod supporting the hand. B gives an enlarged view of the glass capsule. 



be determined readily in terms of a column of water, but it 

 is obvious that for any given vein this pressure will vary with 

 the position of the vein. When the hand hangs pendent at 

 the side the pressure within its veins will be greater than when 

 the hand is raised to the heart-level. The pressure actually 

 measured for any given position of the hand or foot must, 



* Hooker, "American Journal of Physiology," 35, 73, 1914; also Eyster and 

 Hooker, "Johns Hopkins Hospital Bulletin," 274, 1908. 



