LXV.] MOVEMENTS OF THE CHEST WALL. 309 



cardiac impulse, the tracing will show also the number of beats of 

 the heart (fig. 232). 



B. Man. (6.) Stethograph (Marey's). Cause a person to 

 expose his chest. Raise the screw (y) of the stethograph, and fix 



FIG. 232. Stethograph Tracing of a Rabbit. The tracing shows undulations due to 

 the beats of the heart. T indicates time in seconds. 



the plate (/) of the instrument on the exposed chest, with tapes 

 attached to c and d. Depress </, connect the tube (a) with a 

 recording tambour, with the same precautions as in 1, A., and 

 take a tracing (fig. 234). 'Examine the tracing, noting the relation 

 between inspiration and expiration. 



(c.) Polygraph (Rotlte). Use the polygraph of Rothe, record 



Flo. 233. Marey's Stethograph. 



the respiratory movements by means of the bag (fig. 208, A), and 

 study the tracing (fig. 234). 



2. Elasticity of the Lungs. 



Remove the whole of the front of the chest in the rabbit 

 already used. Observe the collapsed lungs. To the tracheal 



