280 



RESPIRATION 



from the neck. Attached to the inner end of one bar is a tambour and ivory 

 button, to the end of the other an ivory button. The apparatus is suspended 

 with the transverse bar posteriorly, the button of the tambour is placed on the 

 part of the chest the movement of which it is desired to record, and the other but- 

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



FIG. 231. Stethograph or Pneumograph. 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.) 



is held as between a pair of calipers. The receiving tambour is connected 

 through a T-piece with a recording tambour of Marey's and with a bulb by 

 means of which air can be squeezed into the cavity of the typanum. When 

 adjusted 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. 



FIG. 232. Tracing of Thoracic Respiratory Movements obtained by means of 

 Marey's Pneumograph. (Foster.) A whole respiratory phase is comprised between a 

 and a; inspiration during which the lever descends, extending from a to b, and expiration 

 from b to a. The undulations at c are caused by the heart's beat. 



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

 consists 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 pressure of air in the bag,. 



