XIII 



EESPIEATORY RHYTHM 



501 



below the threshold, at which the external and internal stimuli 

 are inadequate to throw the central organs into excitation ; the 

 groups appear when, owing to rise of excitability, the external and 

 internal stimuli again become effective (Luciani, 1879). The 

 same theory of periodic respiration was formulated almost 

 simultaneously by Rosenbach (1880) ; by Sokolow and Luchsiiiger 



FIG. 236. Oscillations of tone in respiratory muscles in rabbit poisoned with piridine. (Mosso.) 

 R, respirations recorded with a Marey's tambour applied to xiphoid process. P, tracing of 

 blood pressure in carotid, recorded simultaneously with a mercury manometer. The pro- 

 nounced oscillations of respiration are seen not to be associated with perceptible altera- 

 tions of blood pressure. 



(1880), who endeavoured to reinforce it by ingenious marshalling 

 of the facts ; by Langendorff and Siebert (1881), who confirmed 

 and developed the work of their predecessors ; lastly, by A. Mosso 

 (1885), who resumed and consolidated it by new observations. 



FIG. 237. Thoracic respiration in sleep of robust subject, recorded with Marey's pneumograph ; 

 shows periodic oscillations of both inspiratory and expiratory excursions. (A. Mosso.) 



Zuntz (1882) correctly pointed out the great analogy between 

 the classical phenomenon of Cheyne- Stokes respiration and the 

 alternation of sleep and waking. Sleep corresponds with the 

 pause, the waking state with the group. Just as complete 

 awakening is preceded by an ascending phase of waking up, 

 and sleep is preceded by a descending phase of drowsiness, so 

 the Cheyne -Stokes phenomenon shows increase and decrease. 



VOL. i 2 K I 



