CH. XXVI.] 



GRAPHIC RECORD 



RESPIRATlOMS 



3o7 



called Stethographs. In tracings taken with a stethograph applied to 

 the chest-wall of man or animals, the large up-and-down strokes due 

 to respiration have smaller tremors upon them, due to the heart- 

 beats. 



The tracings in fig. 290 were obtained by applying a stetho- 

 graph to a man's chest. During the tracing shown at the top, he 

 was breathing quietly ; during the tracing shown on the next line, 

 he was breathing deeply. 



It is also possible to record the diaphragmatic movements by the 

 insertion of an elastic bag connected with a tambour into the 



FIG. 291. Tracing of the normal diaphragm respirations of rabbit, a, With quick movement of drum ; 

 b, with slow movement. The upstrokes represent inspiration ; the downstrokes, expiration. To 

 be read from left to right. The time tracing in each case represents seconds. (Marckwald.) 



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

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

 isolated strips of the diaphragm. Such a strip attached in the 

 rabbit to the xiphisternal cartilage may be detached, and attached 

 by a thread to a recording lever ; this strip serves as a sample of the 

 diaphragm 



Fig. 291 shows a tracing obtained in this way. 



The variations of intrapleural pressure may be recorded by the 

 introduction of a cannula into the pleural cavity, which is connected 

 with a mercurial manometer. 



The act of inspiring air, especially in women and children, is a 

 little shorter than that of expelling it, and there is commonly a very 



