108 



SPECIAL PHYSIOLOGY 



(12) If the whole apparatus were filled with water instead of air 

 and water, would it make any essential difference in the result? 

 What effect do the variations of the intrathoracic pressure have 

 upon the circulation? 



II. RESPIRATORY PRESSURE. ELASTICITY OF THE LUNGS. 

 PNEUMATOGRAM. 



A. Respiratory Pressure. 



1. Appliances. Operating case; clippers; rabbit board; ether; 

 ether cone; absorbent cotton; rabbit stethograph; kymograph; a 

 small mercury manometer, to the proximal limb of which is attached 

 a thick-walled rubber tube, a piece of glass tubing for a mouth-piece ; 

 a screw clamp; chronograph; two recording tambours; rabbit. 



2. Preparation. Fix the' rabbit to the operating board and anaes- 

 thetize; clip the ventral surface of the neck. Join up the manometer 

 as shown below. 



FIG. 57 



Tracheal cannula, with manometer attached. 



3. Operation. Make a longitudinal incision over the trachea, 

 through skin and connective tissue. Part the sternothyroid muscles 

 in the median line and expose the trachea. Separate the trachea 

 from the oesophagus and other surrounding tissues for 3 cm. below 

 the larynx. 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 I (Fig. 57). 

 Ligate. 



4. Observations. Respiratory Pressure. The Pneumatogram. (1) 

 After the ligature is tied how does the rabbit breathe? Are the 



