258 



RESPIRATION 



at one end. At the free end of the bars is attached a leather strap, by means of which 

 the apparatus may be suspended 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 button is 

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



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, produced by the movements of the chest, are communicated 



FIG. 232. Tracing of Thoracic Respiratory Movements obtained by means of Marey's Pneu- 

 mograph. (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. 



to a recording tambour. This principle is applied in a modified form in Marey's pneumo- 

 graph, figure 231. 



The variations of intrapleural pressure may be recorded by introducing a cannula into 

 the pleural or pericardial cavity. The cannula should be previously connected with a 

 mercury or other form of manometer by tubing filled with physiological saline. 



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

 ments. This can be done by inserting a receiving tambour into the abdomen below the 

 diaphragm, by the insertion of needles into different parts of the diaphragm and recording 

 the movement of the free ends of needles about the fulcrum formed where the chest wall 

 is pierced, or by recording the contraction of isolated strips of the diaphragm directly. 

 These records all give an accurate picture of the movements of the diaphragm. 



The Relative Time of Inspiration and Expiration and the Respira- 

 tory Movement. The acts of inspiration and expiration take up, un- 

 der ordinary circumstances, a nearly equal time. The time of inspiration, 

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

 expiration, and there is commonly a very slight pause between the end of 

 expiration and the beginning of the next inspiration, see figure 232. The 

 ratio of the respiratory rhythm may be thus expressed: 



Inspiration 6 



Expiration 7 to 8 



Pause Very slight 



