214 SPECIAL PHYSIOLOGY 



(c) Why should you not use curare as an anaesthetic if the poisoned 

 animal does not react to painful stimuli? 



(5) Make two muscle-nerve preparations as described on page 48. 

 Dip the nerve of one and the muscle of the other into curare solution. 

 The parts of the preparation not immersed should be kept moist with 

 normal saline solution. After several minutes mount specimens in 

 the myograph. Stimulate the nerves and note: 



(a) The relative reaction of the gastrocnemii to indirect stimu- 

 lation. 



(6) Does this bear a resemblance to any previous experiment? 

 (c) How do results compare with those of previous experiments? 

 (6) Stimulate the same muscles directly? 



(a) Relative reaction. 



(6) Taking this in connection with the preceding experiment, 

 where have you proven that curare acts? 



(c) How do experiments (5) and (6) compare with experiments 

 (3) and (4)? 1 



V. THE ACTION OF VERATRIN UPON THE NERVOUS SYSTEM. 



1. Materials. Sulphate of veratrin; one dog; three frogs. 



2. Preparation. Prepare a solution of veratrin, 50 mg. to 10 c.c. 

 Pith frogs. Restrain dog, but do not fasten to board. Set up myo- 

 graph and induction coil, the latter arranged for single-induction 

 shocks. 



3. Experiments and Observations. (1) Give subcutaneous injec- 

 tion of 1 mg. per kg. veratrin to the dog. 



(a) Describe symptoms as they arise. 

 (6) Summarize. 



(2) Place thread around the sacral plexus of the pithed frog so as 

 to easily find it, as described under strychnine. Inject 0.003 grm. 

 veratrin into dorsal lymph space. 



(a) Describe symptoms referable to reflexes. 

 (6) Note particularly the difference between a forcible contraction 

 and a prolonged contraction. 



(3) Sever the sacral plexus around which the thread has been 

 passed. 



1 Failure in experiments (5) and (6) may result from insufficient immersion of muscle in 

 curare solution, capillary attraction resulting in the curare reaching muscle supposed to be 

 free from poison, and drying of parts not immersed in solution. Of these the first is by far 

 the most frequent cause of failure, and the sheath of the muscle rendering the absorption of 

 poison a slow process. It may be overcome by making a few slight incisions in sheath, or 

 injecting a drop of the curare solution directly into the muscle. 



The immersed nerve preparation often fails through death of nerve. 



Failure of experiment (2), and consequently (3) and (4), may result from ligature around 

 thigh being not tight enough to prevent diffusion of curare into gastrocnemius. 



