XIII 



RESPIRATORY RHYTHM 



449 



with vaseline) is applied to the floor of the fourth ventricle, it is 

 seen after a few seconds or minutes, according to the rapidity of 

 absorption, that all respiratory movements cease and the thorax is 

 fixed in the cadaveric posture. This paralysis of the respiratory 

 movements is preceded by a brief period of excitation, in which 

 the inspiratory movements are exaggerated. Quite different effects 

 are obtained on the heart, the beats being accelerated directly after 

 the application of the poison, as after section of the vagi, or intoxi- 

 cation with atropine, an effect that persists after the respiratory 

 standstill. When the cocaine hydrochloride is applied in the form 

 of an ointment, so that the poison is more slowly and gradually 



j; 

 r 



FIG. 204. Effects of weak (A) and medium (B) electrical excitation of spinal bulb in dog. 

 (Aducco.) Excitation from o to it'. R, Respirations recorded with Marey's pneumograph ; P. 

 arterial pressure traced with Marey's metal manometer ; s", seconds. The inspiratory effects 

 are seen on both tracings. 



absorbed, different phases of modification may be distinguished in 

 the respiratory and cardiac movements. Fig. 205 shows the 

 curves of normal respiration and heart-beat in the dog ; there are 

 four respirations and eighteen heart-beats in 20 seconds. One 

 minute after applying the cocaine to the floor of the fourth 

 ventricle the curve of Fig. 206 is obtained, which shows five less 

 ample respirations and three beats in 20 seconds. Nine minutes 

 after applying the poison the form of respiration is entirely altered 

 (Fig. 207) and has become quite slow. The line of rest of the 

 thorax corresponds with the extreme inspiratory position, which 

 is due, not to an inspiratory tetanus, but to the fact that the ex- 

 pirations only are active, while the inspirations are passive, i.e. they 

 represent the elastic recoil of the thorax to the position of 

 VOL. I 2 c, 



