198 



EXPERIMENTAL PHARMACOLOGY 



Fig. 189. This lung volume and blood-pressure record was taken from a dog by the 

 use of the blood-pressure regulating device shown in Fig. 188. The lung record was 

 taken by means of (positive) artificial respiration (using the tube shown in Fig. 186 and 

 the method illustrated in Fig. 187). The purpose of the. tracing was to show that con- 

 traction or dilatation of the bronchioles is practically entirely independent of the changes 

 in systemic blood-pressure. The slight variations in the course of the carotid pressure 

 tracing were due to the great suddenness of the extensive changes in caliber of the 

 arterioles produced by the action of the drugs, i. e., the contraction of the arterioles 

 occurred slightly quicker than the blood could siphon over through the small pointed 

 cannulas into the beaker. But if no equalizing device had been used the carotid pressure 

 would have risen above the top of the lung tracing. 



