THE CIRCULATION OF THE BLOOD AND LYMPH 113 



causes an increase in the height of the flame. When the 

 part shrinks during diastole, air is drawn in from the flame, 

 which is depressed. Since the speed of the blood in the 



Plethysmocf ram 



Fin. 34. 



FIG. 35. 



FIG. 34. The highest of the three curves is a plethysmographic record taken from 

 the hand ; the second curve is a sphygmogram taken simultaneously from the corre- 

 sponding radial artery ; the lowest (interrupted) curve is the curve of velocity deduced 

 from a comparison of the first two. (Kick. 



FIG. 35. Simultaneous plethysmographic and sphygmographic tracings. 



FIG. 36. CYBULSKI'S ARRANGEMENT FOR RECORDING VARIATIONS IN THB 



VELOCITY OF THE BLOOD. 



A, tube connected with central, B with peripheral end of divided bloodvessel. The 

 blood stands higher in the tube C than in D. A beam of light passing through the 

 meniscus in both tubes is focussed by the lens L on the travelling photographic 

 plate E. The velocity at any moment is deduced from the height of the meniscus in 

 the two tubes C and D. 



veins may be considered constant during the time of an 

 experiment, the rate at which the volume of the part alters 



8 



