248 EXPERIMENTAL PHARMACOLOGY 



nula (one-fourth inch diameter) and connect up the ether 

 bottle (or anesthetic device shown in Fig. 116). Use the 

 great e*t care in giving the ether not to kill the animal. In- 

 to the femoral vein tie a very small injecting cannula (Fig. 

 18) connected to a burette containing caffeine solution 

 (.5/t)- Record the respiration on the drum. 



Open the abdomen over the bladder and insert a bladder 

 cannula (Fig. 23). Arrange the cannula to empty into a 

 graduated cylinder and when all preparations are made 

 wait ten or twenty minutes to record the normal rate of 

 urine secretion. Test this with Fehling's solution. Then 

 cautiously inject one-half cubic centimeter of caffeine so- 

 lution into the vein. "Watch the effects of this on the 

 respiration closely. From time to time as the animal will 



rubber tube 



Washout 



Fig. 227. An easily made glass cannula showing a sliding rubber tube which may 

 be used to open or close the small opening blown in the side of the tube and used as 

 a "washout." 



tolerate it inject more caffeine in one-half cubic centimeter 

 (or smaller) doses. Is there any change in the rate of 

 urine flow? Collect the urine for each ten minute inter- 

 val. Test for reducing bodies again. Is sugar present ! 

 If so, how do you account for it! 



If you have time, consult Fig. 226 to learn the ar- 

 rangement of the vagus, sympathetic and depressor nerves 

 in the neck of the rabbit, and then carefully dissect out 

 these nerves. Using a very small arterial cannula (Figs. 

 22.") and 227) connect the right carotid artery to the ma- 

 nometer and take a blood-pressure tracing. Stimulate tlu- 

 depressor nerve (peripherally) and note the effect. How 

 do you explain this result? Inject more caffeine and see if 



