164 



SPRING-KYMOGRAPH. 



V 



of the pressure-bottle where it joins the lead tube. By having ^this positive 

 pressure, the escape of blood from the artery into the solution of sodium carbonate 

 is to a large extent avoided. When all is ready, the ligature on the cardiac side 



of the cannula is removed, and 

 immediately the float begins to 

 oscillate and inscribe its move- 

 ments upon the recording sur- 

 face. The fluid within the 

 artery exerts pressure laterally 

 upon the sodium carbonate 

 solution, and this in turn trans- 

 mits it to the mercury.] 



[When we have occasion to 

 take a tracing for any length 

 of time, it must be written 

 upon a strip of paper which 

 is moved at a uniform rate 

 in front of the writing- 

 style on the float (Fig. 73). 

 Various arrangements are em- 

 ployed for this purpose, but it 

 is usual to cause a cylinder to 

 revolve so as to unfold a roll or 

 riband of paper placed on a 

 movable bobbin. As the cylin- 

 Fig. 73. der revolves, it gradually winds 



Ludwig's improved form of revolving cylinder, E, off the strip of paper, which is 

 which is moved by the clock-work in the box, kept applied to the revolving 

 A, and regulated by a Foucault's regulator surf ace by ivory friction wheels, 

 placed on the top of the box. The 



disc, D, moved by the clock-work, presses 

 upon the two wheels, n, which can be raised 

 or lowered by the screw, L, thus altering the 

 position of n on Z>, so as to cause the 

 cylinder to rotate at different rates. The 

 cylinder itself can be raised by the handle, v. 

 On the left side of the figure is a mercurial 

 manometer. When the cylinder is used, it is 

 covered with smoked smooth paper. 



In Fick's complicated kymo- 

 graph a long strip of smoked 

 paper is used. The writing- 

 style may consist of a sable 

 brush, or a fine glass pen filled 

 with aniline blue dissolved in 

 water, to which a little alcohol 

 and glycerine are added.] 



[In order to measure the 

 height of the pressure, we 



must know the position of the 

 abscissa or line of no pressure, and it may be recorded at the same time as the 

 blood-pressure or afterwards. ] 



[In Fig. 74, - x is the zero-line or the abscissa, and the height of the vertical 

 lines or ordinates may be measured by the millimetre scale on the left of the 

 figure. The height of the blood-pressure is obtained by drawing ordinates from 

 the curve to the abscissa, measuring their length, and multiplying by two.} 



(5.) Spring-Kymograph. A. Fick (1864) constructed a " spring-kymo- 

 graph" on the principle of Bourdon's manometer (Fig. 72, II). 



A hollow C-shaped metallic spring, F, is filled with alcohol. One end of the 

 hollow spring is closed, and the other end, covered by a membrane, is brought into 

 connection with a blood-vessel by a junction-piece filled with a solution of sodium 

 carbonate. As soon as the communication with the artery is opened, the pressure 

 rises, and the spring, of course, tends to straighten itself. To the closed end, &, 



