510 CIRCULATION OF BLOOD AND LYMPH. 



as 15 centimeters, von Recklinghausen proposes the level 

 made by a dorsoventral line drawn from the bottom of the 

 sternum (costal angle) to the spinal column. This author* has 

 devised a simple apparatus for determining venous and capillary 

 pressures, the principle of which is shown by the schema repre- 

 sented in Fig. 206. 



A circular bag of thin rubber with a diameter of about 5j cm. is provided 

 with a central opening of 2 cm. The bag is connected with a pump so that 

 it can be blown up, and the degree of pressure exerted is measured by an 

 attached manometer. This bag, moistened with glycerine, is laid upon a 

 vein, as represented in the diagram. It is covered by a glass plate held firmly 

 in position and the bag is then blown up until the vein disappears; the pressure 

 at which this happens is shown by the manometer and marks the pressure 



Fig. 206. To illustrate the method of measuring venous pressure: H, The back of 

 the hand in which a single vein is represented; B, the circular rubber bag with central 

 opening, and with a tube, T, which leads to the pump and the manometer; G, glass plate 

 held over the rubber bag. The bag, B, is blown up by pressure through the tube T until 

 the vein is collapsed. The pressure at which this occurs, or the pressure at which the 

 vein reappears as the bag is allowed to empty, gives the pressure within the vein. (von 

 Recklinghausen.) 



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 

 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, 

 therefore, be corrected for the heart-level by determining the 

 vertical distance between the vein and the heart (costal angle), 

 and subtracting this distance, expressed in centimeters, from 



* Von Recklinghausen, "Archiv f. exper. Pathol. u. Pharmakol.," 55, 470, 

 1906. 



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

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



