100 EXPERIMENTAL PHARMACOLOGY 



ing obtained. Be sure the drum is wound up and set for 

 a slow speed. 



Start the drum and take two inches of normal record. 



2. Stimulate the right vagus nerve (the drum is kept 

 going) with a moderately strong tetanizing current. What 

 are the effects on blood-pressure and respiration? How 

 do you explain this! 



3. Open the left eye and while observing the pupil closely 

 stimulate the left vagus nerve. What do you observe? 

 How do you explain this? Repeat this on the right side. 



4. Crowd on the ether vapor by shutting off the straight 

 end (for air) of the tracheal cannula and shaking up the 

 ether in the bottle. The dog thus breathes a very concen- 

 trated vapor. What effect has this on the respiration and 

 blood-pressure? Do the heart beats become slower? Can 

 you determine this with a mercury manometer? Increase 

 in the amplitude (up and down) of the manometer strokes 

 indicates a slowing of the heart. Why? What mechanical 

 factors are involved? Do not mistake the reflected effects 

 of respiration on the blood-pressure for a change in the 

 amplitude of each separate heart beat. Allow the animal 

 to return to normal. Stimulate the vagi nerves. Are they 

 more or less active in affecting the heart and respiration 

 than before? What nerves are concerned in these respira- 

 tory effects and over what paths do the impulses travel? 

 At what points might an excess of ether affect these? 



5. Give the animal a few breaths of chloroform vapor. 

 This is best done by taking an empty ether bottle (1 pint 

 milk bottle) and putting about two cubic centimeters of 

 chloroform into it (Fig. 89). The cork of the ether bot- 

 tle connected to the dog is now removed and inserted into 

 the second bottle. The chloroform vapor will be quickly 

 inhaled by the animal and there will be an immediate change 

 in the blood-pressure and respiration. Do not allow these 

 changes to go too far. Remove the chloroform bottle and 

 allow the dog to recover. Replace the ether. This may be 



