XIII 



EESPIEATOKY EHYTHM 



455 



on a revolving drum) from a tracheotomised dog which had 3 

 grms. of chloral hydrate injected in several doses into its jugular 

 vein. Under these conditions there are seen to be a few active 

 abdominal expirations, in which one very energetic and one 

 shallow effort alternate with tolerable regularity. All the 



FIG. 209. Thoracic (T) and abdominal (A) pneumograms obtained from two exploring button 

 tambours on a dog, after intravenous injection of 8 grms. chloral hydrate. (Aducco.) The 

 descending curves of A correspond to active abdominal expirations. The slight movements 

 of T are passive. 



respiratory processes depend upon these rhythmical abdominal 

 respirations which pull upon the thoracic walls, on which the 

 traction of the rectal abdominal muscles follows passively. In 

 this case, therefore, the 

 chloral succeeds (tempor- 

 arily at least) in paralys- 

 ing the rhythmic activity 

 of the thoracic inspiratory 

 and expiratory centres, 

 while maintaining and 

 even increasing the action 

 of the expiratory centres 

 for the abdominal muscles. 

 In other cases (in which 

 the specific mechanism of 

 action is unknown) the 

 chloral paralyses both the 

 inspiratory and expiratory 

 abdominal centres, and 

 increases the rhythmical 

 activity of the thoracic expiratory centres. Thecurvesof Fig. 210were 

 taken from a tracheotomised dog, after injecting 5 grms. of chloral 

 hydrate into the jugular vein. It will be seen that the resting 

 position of the thorax coincides with the end of inspiration and 

 commencement of expiration ; between the first and second there is 

 a pause, after which a marked depression of the thorax occurs, which 



pio> 210 ._ Tracing , as iu last flgunji Prom dog after 



intravenous injection of 5 grms. of chloral hydrate. 

 (Aducco.) The descending lines of tracing T coincide 

 with active thoracic expirations, followed immediately 

 b y the ascending lines of passive inspiration. The 



^ verste abdomina f moveill ents (A) are passive. 



