232 



EXPERIMENTAL PHARMACOLOGY 



i 



Fig. 2\>. Tracings from the gastrocnemius muscle of a frog injected with picrotoxine. 



one-half milligram). Wait about three to five minutes for 

 the drug to be absorbed, then start the drum at a moderate 

 rate of speed. After a short time the frog will begin to 

 manifest certain symptoms. Record these (on the lower 

 part of the drum the muscle contraction record should 

 have an amplitude of about one and one-half or two inches) 

 and when the first round of the drum is completed lower 

 it and wait a short while. Then take a second round of 

 contractions on the upper half of the drum. How do the 

 last contractions compare with the first ones obtained'? 

 Have you studied any other drug having a similar action? 

 How do you explain the results'? 



Note. A method for destroying (cutting off) the cerebrum while leav- 

 ing the medulla intact is described on page 238. 



