PLATE LXXXVIF. 



FI<:. 2126. Natural pills 



FIG. 213. Percussion waves ( 41.) 



FUJ. 214. Tracings showing the contractions and expansions of an india-rubber till*, along wliich water is 

 propelled in an intermitting stream by squeezing with the hiind at regular intervals of time an elastic twig 

 provided with valves, with which the tube is in coinmunicati -n ; the bag thus represent* the heart. The thm- 

 tracings are drawn simultaneously, and exhibit the expansive movements of the tube at three different di* 

 tances from the liag, the npper tracing lieing taken at the greatest distance ( 41). 



