236 EXPERIMENTAL PHARMACOLOGY 



of the experiment. The injecting burettes contain adrena- 

 lin and picrotoxine (one cubic centimeter equals one-half 

 milligram). 



When the operations are completed adjust the writing- 

 points on the drum and take a normal record. Stimulate 

 each vagus nerve and get records. How does this affect 

 the respiration and circulation! Now inject one cubic 

 centimeter of picrotoxine and get records of the results. 

 Note the time of day. Inject more picrotoxine from time 

 to time in small doses (one-half or one cubic centimeter) 

 and keep a close watch on the heart action as shown by 

 the amplitude of the manometer tracing and by the rate 

 of heart beat. There should be a slowing of the heart 

 and a fall of pressure. Both of these should be brought 

 on very slowly and cautiously by small repeated doses. 

 (Too large a dose of chloretone weakens the heart con- 

 siderably and must be watched in this experiment. It also 

 depresses the medulla somewhat.) The heart beat should 

 become slow r enough after a time to give a pressure trac- 

 ing with an amplitude of about ten or twelve millimeters 

 (one-half inch) to each stroke of the manometer pointer. 

 When this stage is reached lift up both vagi and tie the 

 ligatures tightly. Does this affect the heart? If not quickly 

 cut both vagi centrally to the ligatures. Does this affect 

 the blood-pressure? Does the respiration remain normal? 

 How do you account for any changes observed? Did you 

 get satisfactory records of all these changes? If not why 

 did you fail ? Can you do better next time ? 



Now stimulate the central end of one vagus nerve. How 

 does this affect the animal ? What nervous paths are con- 

 cerned in this? Stimulate the peripheral end of the nerve 

 and note the effect. 



Inject more picrotoxine. How does the action here com- 

 pare with that in the frog? Inject some adrenaline. Do 

 you get normal effects from this dose? Is the heart 



