RESPIRATION. 



the right side. Connect the catheter with the recording tambour 

 (see Fig. 37), and the movements of the diaphragm will be recorded 

 upon a drum revolving at medium speed. 



(a) First take a tracing of the normal movements of the dia- 

 phragm. Take a time tracing in conjunction with the respiratory 

 tracing. Note the rate of the respirations in the rabbit. These 

 may be influenced by the morphine which has been previously 

 given the rabbit. 



(b) While the tracing is being taken, tickle the rabbit's nose 

 with a feather. Is there any effect on the respiratory movements ? 

 What nerve has been stimulated ? 



Note the movements of the rabbit's nostrils with inspiration and 

 expiration. These movements continue, even though breathing is 

 no longer taking place through the nose, but through the tracheal 

 cannula. Other associated movements you have already noted, 

 e.g., the opening and closing of the glottis. 



(c) Pinch the skin or pour a little ether on the shaved abdom- 

 inal surface. What effect has cutaneous stimulation on respiratory 

 movements ? 



(d) Now tie one vagus with two ligatures and cut between. 

 Mark on the tracing the time at which the vagus was tied and cut. 

 Note any change in the respiratory movements occurring at the 

 time of tying and cutting the nerve or following this operation. If 

 the respiratory rhythm has been disturbed, does it return to nor- 

 mal, after a time ? 



(e) Allow "five or ten minutes to elapse and then stimulate the 

 central end of the cut vagus with a weak tetanizing current. What 

 is the effect on the respiratory movements ? 



(/) Stimulate the central end of the cut vagus with a medium 

 strong tetanizing current. Compare this effect with that obtained 

 with the weak stimulation. 



(g) Apply to the central end of the cut nerve a few crystals of 

 NaCl. Note the change in the respiratory movements. After the 

 effect of this stimulus is sufficiently evident, cut off the small piece 

 of nerve to which the salt has been applied. 



