594 EFFECTS OF DISTENSION AND COLLAPSE. [BOOK n. 



the other hand the trachea be suddenly closed at the end of an 

 expiration (Fig. 82 B), when the lungs have returned to their 

 emptied condition, the result is an increase of the sequent in- 

 spirations, that is to say, an augmentation of inspiratory impulses. 

 If the chest or if the lung only be gently inflated a temporary 

 cessation of all inspiration may be produced, accompanied some- 

 times by an attempt at expiration. If on the other hand air be 



i i i i i 



FIG. 83. EFFECTS OF REPEATED INFLATIONS. POSITIVE VENTILATION. (Head.) 



The lower curve is described, as in Fig. 82, by a lever attached to a slip of the 

 diaphragm. The upper curve shews the inflations from x to y, which were made 

 without any attempt to draw the air out at each inflation ; each rise on this curve 

 denotes an inflation. It will be observed that as the inflations are continued the 

 respiratory movements of the diaphragm are gradually "knocked down." 



sucked out of the chest, or if one lung be made to collapse by 

 puncture of one pleural chamber, a prolonged inspiration is the 

 frequent result, the diaphragm being thrown into a prolonged 

 inspiratory tetanus. If the lungs are repeatedly inflated, without 

 any means being taken to draw out the air after each inflation 



FIG. 84. EFFECTS OF REPEATED SUCTIONS OF THE LUNGS. NEGATIVE 

 VENTILATION. (Head.) 



The curve corresponds exactly to Fig. 83, except that the lungs are subjected to 

 repeated suctions without corresponding inflations. The result is that the inspira- 

 tions are repeated in such a way as to lead almost to an inspiratory tetanus of the 

 diaphragm. 



