THE PHYSIOLOGY OF THE NERVOUS SYSTEM 213 



(a) Record the condition of the dog 1 just before and every ten 

 minutes after injections of curare, with special reference to: 

 (I) Muscular activity. 

 (II) Respiration, number and depth. 



(III) Circulation, rate and rhythm of heart beat. 



(IV) Which stops sooner, respiration or circulation? 

 (6) Formulate the total effect of curare upon the animal. 



(2) Ligate the thigh of a frog, except the sciatic nerve near the 

 knee-joint. Inject into the dorsal lymph space 0.002 grm. curare. 



(a) What elements enter into the formation of a reflex arc ? 



(b) What motor phenomena would result from increased irrita- 

 bility of any part of the reflex arc? 



(c) What motor phenomena would result from lessened irritability 

 or destruction of any element in the reflex arc? 



(d) What effect has the ligature of the thigh on the distribution 

 of the curare? 



(e) How do the reflex arcs, of which the gastrocnemii are the motor 

 ends, differ with regard to the distribution of the curare? What 

 part of the reflex arc is protected from curare in the ligatured limb ? 



(/) Describe the relative reaction of the gastrocnemii to stimuli 

 (chemical, mechanical, electric) applied to the various parts of the 

 body and limbs. 



(g) Is the sensorium intact? Is it reached by the curare? 



(h) Is the cord intact? Is it reached by curare? 



(3) Expose the sciatic nerves, near the body, in the frog, used in 

 the experiment. Stimulate them. 



(a) What elements in the reflex arc enter into consideration in 

 this experiment? 



(b) Which of these elements are exposed to, which protected from, 

 the poison? 



(c) Are both sciatics reached by curare? 



(d) Is there a difference in the reaction of the gastrocnemii to the 

 stimuli applied to the sciatic nerves? 



(e) To what elements of the reflex arc have you limited the possible 

 action of the curare? 



(/) Have you proven that curare does not affect the nerve trunks ? 



(4) Expose gastrocnemii by cutaneous incision. Stimulate the 

 muscles directly. 



(a) Is there a difference in reaction to stimuli? 



(b) If a muscle in a poisoned animal reacts to direct stimuli, but 

 not to indirect stimuli, though the nerve fibres be proven to be intact, 

 on what element in the reflex arc must the poison act? 



1 On dog: Voluntary muscles first paralyzed, then semivoluntary, e.g., respiration. Stu- 

 dents have maintained life for forty minutes by artificial respiration after respiratory 

 paralysis, the heart's action being normally strong after complete respiratory paralysis. 



