BLOOD PRESSURE 375 



The compression of the vein can also be accomplished by means 

 of a spring manometer such as was first employed by von Frey,^ or 

 by means of a cuff connected with a water manometer. Frank and 

 Reh,2 for example, use two cuffs, one of which is applied to the fore- 

 arm and the other to the arm. The former is inflated so as to fit 

 snugly, but without exerting a pressure of more than 1 cm. H2O. 

 The arm-cuff is then inflated slowly until the pressure in the manometer 

 connected with the lower cuff, is suddenly seen to rise. This change 

 is taken to indicate an increase in the volume of the arm caused by the 

 obstruction to the venous return distally to the arm cuff. When this 

 obstruction first becomes evident, the pressure in the distal cuff must 

 equal the venous pressure. Obviously, these determinations must 

 either be made at the level of the heart or must be corrected for this 

 level, because the pressure in any vein varies with its position. Thus, 

 if the arm is allowed to hang pendant at the side, the pressure in the 



Fig. 195. — Method of Measuring Venous Blood-pressure. 

 The rubber capsule is adjusted upon the vein and is covered with a glass plate or 

 small box glued to the surface with collodion. The capsule is connected with a ma- 

 nometer and pressure-bulb. (,v. Recklinghausen.) 



veins of the hand is much greater than when it is elevated to a point 

 above the heart. 



Gartner^ has advised the following procedure. If the arm is 

 slowly raised, the veins of the hand collapse as soon as a certain level 

 has been reached. If the distance between this level and that of the 

 heart at the junction of the fifth costal cartilage with the sternum is 

 now measured, we obtain the pressure supporting the blood at the 

 right auricle in centimeters of blood, or water, because 10 cm. of blood 

 equal 10.6 cm. of water. Moritz and Tabora"^ have called attention 

 to the fact that the venous pressure corresponds to the pressure neces- 

 sary to cause normal saline solution to enter the body. If the infusion 

 is made through the median vein of the arm when placed at the level 

 of the heart, the pressure in this vein must correspond to the height 

 of the column of saline solution still left in the buret at the end of the 

 injection. It is of interest to note that the values obtained with the 



1 Deutsch. Archiv fiir klin. Med., Ixxiii, 1902. 



^Zeitschr. fiir Exp. Path, und Therap., 1912; also see: A. A. Howell in Arch, 

 fiir int. med., ix, 1912. 



3 Miinchener med. Wochenschr., Ixxlv, 1904. 

 * Deutsch. Archiv fiir klin. Med., xcviii, 1910. 



