CH. XXIV.] 



STETHOGRAPHS 



355 



A simpler form of this apparatus consists of a thick india-rubber bag of ellipti- 

 hape about three inches long, to one end of which a rigid gutta-percha tube is 



cal shape 



FIG. 328. Stethograph. h, tambour fixed at right angles to plate of steel/; c and d, arms by which 

 instrument is attached to chest by belt e. When the chest expands, the arms are pulled asunder, 

 which bends the steel plate, and the tambour is affected by the pressure of &, which is attached to 

 it on the one hand, and to the upright in connection with horizontal screw g. (Modified from 

 Marey's instrument.) 



attached. This bag may be fixed at any required place on the chest by means of a 

 strap and buckle. By means of the gutta-percha tube the variations of the pres- 



Tambour. 

 fvory^button. 



Tube to communi- 

 cate with record- 

 ing tambour. 



Ball to fill apparatus 

 with'air. 



FIG. 329. Stethograph. (Burdon-Sanderson.) 



