THE TIME RELATIONS OF RESPIRATORY MOVEMENTS. 



209 



with two openings in its walls. The trachea of the animal having been previously 

 cut across, a cannula is fastened in the pulmonary end, and is attached to a tube 

 passing through one of the openings in the chamber (respiration being conducted 

 undisturbed through this tube) . Through the other opening passes a manometer- 

 tube, filled with water, and pro- 

 vided with a recording float. The 

 same experiment may be conducted 

 with a human subject, provided the 

 breathing tube be placed in the 

 mouth and the nose be held closed. 

 Gad (Fig. 78) has succeeded in re- 

 cording graphically the variations in 

 the volume of the respired air by 

 means of an apparatus: the expired 

 air lifts a light, balanced box, which 

 is closed off by water. In rising, 

 this box moves a recording lever. 

 During inspiration the box sinks. 



3. The variations in the rapidity FIG. 78. Air-volume Recorder (Pneumoplethysmograph) 

 with which the respiratory gases are (after Gad), 



changed may be recorded as follows : 



A tube is fastened in the trachea of an animal, or in the mouth of a human 

 subject (holding the nostrils closed), in the same way as with the dromograph 

 (Fig. 69) . The pendulum (made broader for this purpose) will swing to and fro 

 during inspiration and expiration, and will record the velocity of the currents of 

 air entering and leaving the lungs. 



FIG. 79.-Pneumatograms Recorded by Means of Riegel's Stethograph: /, normal curve; {. ]nsflrr , 

 with emphysema; a, inspiratory limb, b t summit, c, expiratory limb of the curve. The small elevations are due 

 to the pulsations of the heart. 



The curve in Fig. 77 B was drawn upon a vibrating tuning-fork plate, by 

 means of the air-cushion of Brondgeest's pansphygmograph, applied to t 

 form process of a health v man. The inspiration (ascending limb) beg 

 moderate rapidity, is accelerated in the middle, and again becomes slower towar 



14 



