RESPIRATION 205 



it is increased and in expiration diminished. This tambour is in 

 communication with another, which is provided with a writing lever 

 (Marey's pneumograph, Sanderson's stethometer, Brondgeest's pan- 

 sphygmograph). (Fig. 77.) Or an elastic tube, with a spiral spring 

 in its lumen, may be fastened around the thorax or abdomen and 

 connected with a piston-recorder (a small cylinder in which works a 

 piston carrying a writing-point) (Fitz). 



(2) By recording the changes of pressure produced in the air- 

 passages by the respiratory movements. This can be done by con- 

 necting a cannula in the trachea of an animal with a recording 

 tambour in the manner described in the Practical Exercise:!, p. 272. 

 The changes .of pressure may be measured by connecting a mano- 

 meter with the trachea, or in man with the nostril. 



(3) By writing off the changes of pressure which occur in the 

 thoracic cavity during respiration. For this purpose a trocar is 



FIG. 78. 



The upper tracing is a record of the respiratory movements in a rabbit, taken with 

 Kronecker's lever between the diaphragm and liver. The lower curve is a blood- 

 pressure tracing showing large oscillations (like Traube-Hering waves). E, expiration ; 

 I, inspiration. Time trace, seconds. The animal was under the influence of gelsemin. 



introduced through an intercostal space into one of the pleural sacs, 

 without the admission of air, or into the pericardium, and then con- 

 nected with a manometer or other recording apparatus. Or a tube, 

 similar in construction to a cardiac sound (p. 86), and, like it, 

 terminating in an elastic bag, may be pushed down the oesophagus. 

 The variations in the intra-thoracic pressure are transmitted to the 

 air in the bag, and thence to a tambour connected with the sound. 



When the respiratory movements are studied in any of 

 these ways, it is found that there is practically no pause 

 between the end of inspiration and the beginning of expira- 

 tion. Nor, although the chest collapses more gradually 

 than it expands, is there any distinct interval in ordinary 





