METHODS FOR MEASURING THE BLOOD-PRESSURE. ^3 



namely the curved line, the abscissa {base) and the initial and terminal ordin 



obtained by counting the squares. A. W. Volkmann cut out the cuTe-ar^a and 

 weighed it, and then compared with it the rectangle made from the 

 and havinp- the samp Kac^-lin^ m +v,~4- ,> ~-n.:.. j_ & , 



1 1 to 



which is frequently attached to steam-engines 



A hollow spring bent in the shape of the 'letter C (F) and filled with alcohol 



FIG. 65. I, Carl Ludwig's Kymograph; II, Adolph Pick's hollow-spring kymograph; III, blood- pressure curves 

 (above) and respiratory curves (below), traced at the same time (after C. Ludwig and Einbrodt). 



is brought into connection at its lower extremity (a) with the lateral wall of the 

 artery (x x) by means of a suitable cannula, while the other extremity of the 

 spring is closed. As soon as the internal pressure is increased, the bent spring 

 is straightened out. The closed extremity (b) is connected with an upright 

 rod (g), which acts on a system of writing-levers (hike) composed of delicate 

 pieces of reed, which records the variations in pressure on a moving recording 

 surface. Both the blood-pressure and the variations in the pulse are recorded; 

 the latter, however, without their characteristic peculiarities. Hiirthle reduced 

 the apparatus to one-fourth of its original size, in which form the results 

 recorded are quite accurate because of the slight displacement of fluid. 



5. A. Pick's Flat-spring Kymograph (Fig. 66) has been used in preference to 

 any other by its inventor since 1885. A tube, i mm. thick and filled with air (Fig. 

 66, a a), communicates with the blood-vessel by means of a cannula (c), and 

 ends in an excavated expansion covered with a rubber membrane, from which a 

 point (s) projects downward. The latter presses upon a tightly stretched hori- 



