290 



EXPERIMENTAL PHARMACOLOGY 



thus holds the chest open. As soon as the chest is opened 

 artificial (positive) respiration is begun. Two forms of 

 apparatus for thus giving ether to an animal are shown in 

 Figs. 53 and 107. The artificial respiration thus begun 

 is kept up throughout the experiment if only positive pres- 

 sure is available. But if negative (interrupted) pressure 

 is available this is substituted immediately after tlie ani- 

 mal is pitlied. 



If positive pressure is used then the closed chest acts as 



^-Adjustable by-pass 



Fig. 257. Adjustment of the apparatus shown in Fig. 255 in the chest of a dog. 

 The sawed edge of the sternum catches against the flange of the apparatus and the skin 

 and fascia are brought up and clamped tightly with hemostats to the edges of the plate. 

 One or two stitches may be taken to draw the chest together at the front end of the 

 ?nparatus. If '-nsi ; ve artificial respiration is used this apparatus simply converts the 

 chest into a rigid-walled plethysmograph or oncometer for the lungs and heart. A glass 

 (or celluloid) window aids greatly by allowing the operator to see when the lungs are 

 being sufficiently inflated. 



an oncometer and the tube to the recording tambour (which 

 should have a large bowl) is connected to the tube labeled 

 "aspirate' 1 in Fig. 255. Thus when the lungs are blown 

 full of air through the trachea and are thus expanded air 

 will be forced out of the chest and into the tambour the 

 pointer of which will rise. Conversely when the lungs col- 



