482 EFFECTS OF DISTENSION AND COLLAPSE. [Book ii. 



the lungs have returned to their emptied condition, the result 

 is an increase of the sequent inspirations, 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 sometimes by an 

 attempt at expiration. If on the other hand air be sucked out 

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



J — I — I — II I I I l_! 1 ''I''' 1 l_l I i 1 I I I I I I I I I I — I — 1_L 



Fig. 97. Effects of repeated Inflations. Positive ventilation. (Head.) 



The lower curve is described, as in Fig. 96, 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." 



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. 97), a procedure which we may speak of as positive 





Fig. 98. Effects of repeated Suctions of the Lungs. 



ventilation. (Head.) 



Negative 



The curve corresponds exactly to Fig. 97, except that the lungs are subjected 

 to repeated suctions without corresponding inflations. The result is that the 

 inspirations are repeated in such a way as to be led almost to an inspiratory 

 tetanus of the diaphragm. 



