1 64 



METHODS FOR MEASURING THE BLOOD-PRESSURE. 



zontal steel spring (F), which articulates by means of a connecting piece (b) 

 through two joints (d i} with a writing-lever (H} . The parts of the instrument are 

 held in a metallic frame (R K). In order to determine the absolute values of 

 variations in pressure the apparatus must first be graduated empirically by com- 

 paring it with a mercurial manometer. 



6. Hurthle's Manometer (Fig. 67) is a similar instrument. A small metallic 

 drum (Fig. 67, d) is intercalated in the course of an artery (c c) by means of 

 tubes. The drum is covered with a thin rubber membrane, from the center of 

 which a process (e) projects. The latter is supported by a spring (F), to which,. 



Fio. 66. Adolph Pick's Flat-spring Kymograph. 



at some convenient point that can be varied at will (v), the writing-lever is at- 

 tached. The whole contrivance is attached to a stationary rod (i i) by means 

 of a carrier (T). This apparatus also, like the preceding one, must first be gradu- 

 ated empirically in order to determine in advance the height to which the point 

 (s) of the writing-lever gradually rises with increasing pressure (from o to 

 100 mm. of mercury). 



Hiirthle also constructed a torsion-manometer according to the plan of Rov, 

 the pressure being measured by the torsion of a steel spring. 



B. In man the blood-pressure within an artery can be measured in the sim- 

 plest manner by means of a graduated sphygmograph. The weight that just 



FIG. 67. Hurthle's Kymograph. 



suffices to arrest the movement of the writing-lever corresponds to the tension 

 of the vessel. The radial artery of healthy students examined in this way under 

 Landois' direction and loaded for a distance of i cm. exhibited an average blood- 

 pressure of 550 grams. 



Manometric Method. v. Basch determined the blood-pressure by a mano- 

 metric method, applying his sphygmomanometer to the pulsating vessel. The 

 hollow, air-containing cushion applied to the artery communicates with an aneroid 

 barometer, the pointer of which indicates the pressure. As soon as the pressure 

 indicated by the latter slightly exceeds the pressure in the artery, the latter is 



