528 THE OUTGO OF ENERGY 



hollow tube through which the air waves reach the 

 rubber membrane. A right-angled piece of alumin- 

 ium transmits the motion of the membrane to the 

 writing lever. The moving parts are of the lightest 



Fig. 71. The sphygmograph tambour ; about twice 

 the actual size. 



construction. The axle of the writing lever is held in 

 a yoke, the distance of which from the fulcrum of the 

 lever is readily adjustable. The rubber membrane is 

 not tied, but is held in place by a removable ring, 

 a time-saving device. 



If a small glass thistle-tube placed over the carotid 

 artery be connected with this tambour by a rubber 

 tube, preferably with a side branch, admirable pulse 

 tracings may be recorded. By covering the thistle- 

 tube with a rubber membrane upon which a bone but- 

 ton is cemented, sphygmograms may be taken from 

 the radial artery or from the tubes of the circulation 

 scheme. The same tambour is used with the plethys- 

 mograph tube. 



