XIII 



RESPIRATORY RHYTHM 



455 



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

 grms. of chloral hydrate injected in several closes 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) ami abdominal (A) puenmograms 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 



' FIG. 210. Tracings as in last Injure. 



chloral paralyses both the 



inspiratory and expiratory 



abdominal centres, and 



increases the rhythmical 



activity of the thoracic expiratory centres. Thecurvesof Fig. 21(Kvere 



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 



From dog after 

 intravenous injection of 5 grms. of chloral hydrate. 

 (Aducco.) The descending lines of tracing T coincide 

 with active thoracic expirations, followed immediately 

 by the ascending lines of passive inspiration. The 

 inverse abdominal movements (A) are passive. 



