PHARMACOLOGY. 299 



(4) Ligate the thigh of a pithed frog at the junction 

 with the body, not including in the ligature the sciatic 

 nerve. Sever all tissues just below the ligature ex- 

 cept the nerve and the femur. Carefully separate 

 the cut surfaces with rubber tissue so as to prevent 

 diffusion of the drug. Inject 0.003 gm. veratrin into 

 the dorsal lymph space. 



(#) By means of a diagram show the distribution of 

 the poison. 



() Compare the contractions of the legs, noting par- 

 ticularly the difference in the duration rather than 

 the difference in the force of the contraction. 



(V) If the protected limb reacts normally to stimuli, 

 to what elements in the reflex arc have you limited 

 the possible action of veratrin? 



(</) Compare results with similar experiment with 

 strychnin. 



(5) From the frog used in experiment (4) make two 

 gastrocnemii preparations. Fasten in myograph by 

 means of femurs, and stimulate them directly, making 

 tracings of contractions. 



(a) Compare tracings. 



(/>) To what elements have we limited the action of 



veratrin ? 

 (c) Suggest an experiment which would limit the 



action to one element. 



(6) Very cautiously sniff veratrin. Describe the sensa- 

 sation. 



(7) General observations and comparisons. 



(a) Review your notes on the action of curare, strych- 

 nin and veratrin upon the reflex arc. 



() How would you prove that a drug paralyzed by 

 its action on the spinal cord? 



(<:) How would you prove that a drug destroyed reflex 

 activity by its action on some part of the sensorium? 



