12 



II. What is the Influence of the Nerves upon Skeletal 



Muscles ? 



METHODS. (A) Stimulation of the nerve, and (B) throwing 

 the nerve out of action. 



Connect up a galvanic circuit as in fig. 1 or a Faradic 

 current as in fig. 2, using the pin electrodes provided. 



Always make apparatus ready and see that it is working 

 before preparing the animal. 



The second frog supplied has. been killed by destroying its 

 brain, as in (2). A ligature has then been placed low down, 



FIG. 5. Incisions for Separation of Hind Legs. 



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 pre- 

 vented by the ligature from reaching the terminations of the 

 nerve in the gastrocnemius muscle. 



FIG. 6. Skinning Hind Legs (use cloth round fingers). 



Compare and describe the condition of this frog with the 

 normal one before the cord was destroyed (2). 



What has been the effect of the curare ? 



Remove the anterior part of both frogs by three cuts (fig. 5), 

 taking care that the third cut leaves a piece of the vertebral 



