300 



PHYSIOLOGY. 



crural artery about three inches from her belly, I inserted into it a 

 brass pipe whose bore was one-sixth of an inch in diameter. To 

 that, by means of another brass pipe, which was fitly adapted to it, 

 I fixed a glass tube of nearly the same diameter and which was nine 

 feet in length. Then, untying the ligature on the artery, the blood 

 rose in the tube eight feet three inches perpendicular above the level 

 of the left ventricle of the heart. When the blood was at its full 

 height, it would rise and fall at and after each pulse two, three, or 

 four inches. Sometimes it would fall twelve or fourteen inches, and 

 demonstrate at that point the same up-and-down vibrations, at and 



Fig. 99. Ludwig's Kymograph. (YEO.) 



R, Rotating drum blackened, which is moved by the clockwork inclosed in 

 A by means of the disc, D, pressing on the wheel, n. The cylinder may be 

 elevated or depressed by the screw, v, which is actuated by the handle, 17. 



after each pulse, as it had when it was at its full height. After 

 forty or fifty pulses it would rise to the former height again. 



"Later I took away the glass tube and let the blood from the 

 artery mount up into the open air, when the greatest height of its 

 jet was not above two feet." 



Though the first real truths concerning blood-pressure were 

 thus gained, nevertheless the method was crude and cumbersome in 

 that the blood would soon clot and an eight-foot column of blood 

 was not easily watched in its fluctuations. 



Poiseuille, in 1828 ? introduced into physiological experimenta- 



