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HANDBOOK OF PHYSIOLOGY. 



is made to press upon the corresponding side of the chest, so that the chest is, 

 as it were, held between a pair of calipers. The tambour is connected by 

 tubing and a T piece with a recording tambour of Marey's, and with a ball, 

 by means of which air can be squeezed into the cavity of the tympanum. 

 When in work the tube connected with the air ball is shut off by means of a 

 screw clamp. The movement of the chest is thus communicated to the recording 

 tambour. 



A simpler form of this apparatus, called a pneumograph or stethograph, 

 consisting of a thick India-rubber bag of elliptical shape about three inches 

 long, to one end of which a rigid gutta-percha tube is 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 presssure of air in the 



Tambour. 

 Ivory button. 



Tube to commu- 

 nicate with re- 

 cording tam- 

 bour 



Ball to fill appa- 

 ratus with air. 



Fig. 213. -Stethometer. (Burden Sanderson.) 



bag produced by the movements of the chest are communicated to a recording 

 tambour. This apparatus is a simplified form of Marey's pneumograph (fig. 



The variations of intrapleural pressure may be recorded by the introducton 

 of a canula into the pleural or pericardial cavity, which is connected with a 

 mercurial manometer. 



Finally, it has been found possible in various ways to record the dia- 

 phragmatic movements by the insertion of an elastic bar connected with a 

 tambour into the abdomen below it (phrenograph) , by the insertion of needles 

 into different parts of its structure, or by recording the contraction of isolated 

 strips of the diaphragm. 



The acts of expansion and contraction of the chest take up under 

 ordinary circumstances a nearly equal time. The act of inspiring air, 



