138 INSTRUMENTS FOR INVESTIGATING THE PULSE. 



metallic gutter b, which is placed on the skin so that its concavity covers the 

 artery like a small tunnel. The narrow space between the wall of the tunnel 

 and the skin is filled with illuminating gas. To this end one extremity of the 

 metallic tunnel is connected with the gas-tube g, while the other extremity com- 

 municates by means of a short rubber connecting piece x q with a small tube t, 

 bent upward at an angle and the point of which is drawn out to a minute opening 

 for the escape of the gas. The gas is allowed to pass through the metallic tunnel, 

 under low pressure, the inflow being regulated so that the flame v is not more 

 than a few millimeters long. It is readily seen that the flame increases in height 

 synchronously with each pulse-beat and that the descent is interrupted by a 

 distinct after-beat, von Kries photographed the image of the flame. 



The measurements of the accompany- 

 ing curve are as follows : 



1-2 = 7.5 = 0.121 sec. 

 13 = 16 = 0.258 

 1-4 = 22.5 = 0.363 

 i-5 = 39-5 = - 6 3 8 



FIG. 47. Sphygmographic Tracing from 



Radial Artery Made with Landois' Angiograph 



the 



Attached 5 to a Vibrating Tuning-fork, 

 indentation corresponds to 0.01613 sec. 



Each 



Hem-autography. If a freely exposed artery be divided in an animal so that 

 the blood-stream spurts forth and is allowed to impinge on a glass plate or a sheet 

 of paper moved vertically at some distance, the resulting tracing will coincide 

 almost perfectly with the normal curve of the artery as recorded by the sphygmo- 

 graph. In addition to the primary elevation (Fig. 49, P), the recoil-elevation (R) 

 and the elasticity-elevations (e e) are appreciable. This self-registration of the 



FIG. 48. Landois' Gas-sphygmoscope. 



blood-wave furnishes a convincing proof that the movement is produced in the 

 blood itself and is communicated as an undulatory movement to the arterial wall. 

 By determining the quantity of blood contained in the several portions of the 

 hemautographic tracing it is found that the quantity of blood that escapes from 

 the divided artery during systole is to the quantity that escapes during diastole 

 (that is during contraction and dilatation of the vessel) approximately as 7 : 10. 

 The quantity of blood that escapes during a unit of time while the artery is di- 

 lating is equal to a little more than twice the quantity that escapes during a unit 

 of time while the vessel is contracting. 



THE PULSE-TRACING, THE RECOIL-ELEVATION AND THE 

 ELASTICITY-ELEVATIONS. 



The sphygmogram presents an ascending limb, recorded during the 

 distention (diastole) of the artery; the apex (Fig. 50, P); and the de- 

 scending limb, which corresponds to the contraction (systole) of the 



