356 



RESPIRATION 



[CII. XXIV. 



sure of air in the bag produced by the movements of the chest are communicated 

 to a recording tambour. This apparatus is a simplified form of Marey's stetho- 

 graph (fig. 328). 



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. 



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

 movements by the insertion of an elastic bag connected with a tambour into the 

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

 of its structure, or by recording trie 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 method was largely used by 

 Head ; this strip serves as a sample of the diaphragm. 



Fig. 330 shows a tracing obtained in this way ; but in tracings taken with a 



FIG. 330. 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.) 



stethograph, or any of the numerous arrangements of tambours which are applied to 

 the chest-walls of men and animals, the large up-and-down strokes due to the 

 respiratory movements have upon them smaller waves due to heart-beats. 



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

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

 however, especially in women and children, is a little shorter than 

 that of expelling it, and there is commonly a very slight pause 

 between the end of expiration and the beginning of the next inspira- 

 tion. 



If the ear be placed in contact with the wall of the chest, or be 

 separated from it only by a good conductor of sound or stethoscope, 

 a faint respiratory or vesicular murmur is heard during inspiration. 

 This sound varies somewhat in different parts being loudest or 



