XXX. Respiratory pressure. 



/. Appliances. Operating case; clippers; rabbit board; 

 ether; ether cone; absorbent cotton; rabbit stethograph; 

 kymograph; a small mercury manometer, to the prox- 

 imal limb of which is attached a thick walled rubber 

 tube, a piece of glass tubing for a mouthpiece; a screw 

 clamp; chronograph; two recording tambours; rabbit. 



2. Preparation. Fix and anaesthetize the rabbit, and clip 

 the ventral surface of the neck. Join up the manometer 

 as shown in Fig. 23. 



j>. Operation. Make a longitudinal incision over the 

 trachea. Carefully pass a strong linen ligature under 

 the trachea. Make a median ventral slit in the trachea 

 anterior to the ligature. Pass through the slit the limb 

 of the Y-tube marked 1. (Fig. 23.) Ligate. 



4.. Observations. 



a. Respiratory pressure. The pneumatogram. 



(1) After the ligature is tied how does the rabbit 

 breathe? Are the thoracic and abdominal move- 

 ments of respiration accompanied by other respira- 

 tory movements? 



(2) With tube n (Fig. 23) open is there any variation 

 of the mercury during respiration? 



(3) With a screw clamp slowly close tube n. As 

 the resistance to the flow of air increases what 

 change is noted in the manometer? 



(4) Quickly clamp tube n at end of expiration and 

 carefully note the manometer reading. Is it posi- 

 tive or negative? 



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