ELEMENTARY EXPERIMENTAL PHYSIOLOGY 33 



1. The frog supplied has been killed by destroying its brain. A 

 ligature has then been placed low down, round all the structures of 

 one thigh excepting the sciatic nerve, and a dose of curare has been 

 injected under the skin. The curare has thus 

 acted on the nerve, but has been prevented by 

 the ligature from reaching the gastrocnemius 

 muscle. (Fig. 23.) 



Describe the condition of this frog compared 

 with the normal one before the cord was de- 

 stroyed (p. 29, A. 1). 



What has been the effect of the curare ? 



Expose the sciatic nerve on the side opposite to 

 the ligature (p. 30, 3). That on the ligatured side 

 is already exposed. Now apply the electrodes 

 to the structures indicated below, and stimu- 

 late by closing and opening the mercury key, 

 noting what happens in the muscles. 



(i) Limb exposed to curare (unligatured). 

 (a) Sciatic nerve ; (6) Gastrocnemius muscle. 



(ii) Limb protected (ligatured), (a) Sciatic 

 nerve (above where ligature was applied) ; (b) 

 Gastrocnemius muscle. 



Record the results on the appended table : 



FIG. 23. To show 

 the parts of the 

 frog acted upon 

 by curare 

 (shaded). 

 (From Noel Paton's 

 Essentials.) 



Now formulate your conclusions as to 1. What is the influence 

 of nerve upon skeletal muscle. 2. What is the influence of curare 

 upon (a) nerve, (6) muscle, and (c) the junction of nerve with muscle. 



Can a Muscle be Stimulated without the Intervention of the Nerve ? 

 Try to answer this question from the results of the last experiment. 



E. 



THE STIMULATION OF NERVE AND MUSCLE BY 

 ELECTRICITY 



I. 



The Isolated Nerve-MusclePreparation of the Frog 



1. Galvanic Current. 



Using the galvanic current either from the galvanic terminals of 

 the switch-board, or from two Daniell cells in series with a rheocord 

 in the circuit (Appendix, Fig. 77) with ordinary thick wires, not pin 



D 



