THE CIRCULATION OF THE BLOOD. 



345 



artery at the end of the cardiac diastole; or in other words, the pressure in 

 the manometer from which the greatest oscillation takes place indicates 

 diastolic pressure. These experimenters connected the right carotid artery 

 of a dog with a mercurial manometer, interposing along the course of the 

 connecting tube a maximum and a minimum valve. The left carotid 

 artery was surrounded by a plethysmograph which was connected, with 

 both a mercurial and a spring manometer, the former for the purpose 

 of indicating the pressure necessary to obtain the greatest oscillation, the 

 latter for the purpose of magnifying and recording the pulsation. When 

 the observations were simultaneously made it was found that the diastolic 

 pressure in the right carotid measured by the minimum manometer was 



FIG. 161. STANTON'S SPHYGMOMANOMETER. 



almost exactly equal to the pressure measured by the manometer in connec- 

 tion with the sphygmomanometer surrounding the left carotid artery, when 

 it was exhibiting its maximum excursions. The difference in the results of 

 the two sides scarcely exceeded more than one or two millimeters of mercury. 

 It was, therefore, established that the greatest oscillations record diastolic 

 pressure. It was also shown by the same investigators that Mosso's appara- 

 tus is not adapted for obtaining systolic pressure. * 



Among the many forms of sphygmomanometers adapted for clinic pur- 

 poses and with which both systolic and diastolic pressures may be obtained 

 is that devised by Stanton 1 (Fig. 161). The pressure is applied to the arm by 



1 The following description of this apparatus is abstracted from the Univ. of Pa. Medical 

 Bulletin, Feb., 1903. 



