BLOOD PRESSURE 369 



with the sphygmomanometers devised by Erlanger 1 and Mtinzer 2 or 

 with the sphygmoscope of Bing, 3 or the oscillometer of Widmer. 4 It 

 is true, however, that the greatest number of instruments of this kind 

 are modifications of the Riva-Rocci apparatus 5 described previously. 

 The fundamental principle has remained the same in all cases and only 

 insignificant changes have been made. Thus, it has been shown by 

 direct measurements, that a narrow arm-piece gives somewhat lower 

 values, and hence, a much broader one, measuring 12 cm. in width, is 

 now most commonly employed. In addition, the original mercury- 



FIG. 192. JANEWAY'S SPHYGMOMANOMETER. 



A, folding U tube; B, arm cuff; C, pressure bulb; D and E, needle-valve for release 

 of pressure; F, cork for closing end of mercury tube. 



reservoir has been displaced in several of them by a modern mercury 

 manometer to which a more convenient and patent form has been given 

 so that it can be carried from place to place without spilling the mer- 

 cury. An ordinary valved rubber bulb may be used for the inflation 

 and deflation of the cuff. By using the metal tonometer devised by 

 v. Basch, as a sample, certain instruments have recently been con- 



1 Am. Jour, of Physiol., Proc. xxii, 1902, also ibid., x, 1904. 



2 Munchener med. Wochenschr., 1907, 1357. 



3 Berliner klin. Wochenschr., 1907, 690. 



4 Vaquez, Compt. rend., Ixvi, and Paris medicale, 1911. 



6 Gartner, Wiener med. Wochenschr., xxxi, 1899, and Martin, Munchener med. 

 Wochenschr., xxiv, 1903. 



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