respond, try tin.- sartorius or some other muscle of thi leg. ( ICcker, 

 The Frog, p. <>S. i 



1. Osmotic stimuli, (a) I 'lace a few -alt crystals on the nerve 

 or dip in J 1 ^ m. Xal'l. Result ? Wash off the salt with ph\ -i< (logical 

 salt solution. Result? 



(hi Allow the nerve t dry. What is the effect i n the musele? 

 I >oes the nerve lose its irritability? \\ a>h with salt solution to 

 see if the power of functioning' returns? 



(ci Kern ve a sartorius muscle and suspend it half immersed in 

 distilled water. Note carefully any movements or changes in length 

 >r color? 



i Si i. Independent irritability of muscle. A muscle is stimulated 

 by the electric current, but we cannot be certain that nerves in the 

 muscle are not also stimulated. These nerve endings can be para- 

 lyzed by curare. Proceed as follows: Ktherize a fr g lit/htly with 

 ether soaked in cotton under a glass jar. Kxpose the sciatic nerve 

 in the thigh by a small slit in the skin over the course of the nerve; 

 be- especially careful not to injure the femoral artery which runs 

 close to the nerve. Carefully separate the nerve for a length of half 

 an inch; pass a strong thread under the nerve, and tightly ligature 

 the \vhcle leg except the nerve. The circulation is thus interrupted 

 below the ligature without injury to the nerve. Xow inject into the 

 dorsal lymph sac a few drops of a \' ', solution of curare. When 

 paralysis is complete (15-30 min.i, expose both sciatic nerves and 

 stimulate with tetanizing currents. Xote the difference between the 

 two legs, and explain. Is the nerve trunk affected by the curare? 

 Where i- the point of actim ? Is the muscle itself affected? Stimu- 

 late the curarized muscles directly. Do they contract? What do 

 you conclude a- to the independent irritability of muscle? Place the 

 non-poisoned muscle with its attached nerve, in a watch-glass with 

 curare solution. At intervals test its irritability through the nerve". 

 U it- direct irritability affected? Test the direct irritability of a 

 curarized muscle to the make and break of the constant (or gal- 

 vanic) current. Using non-polarizable electrodes applied at opposite 

 end- of the muscle. Trv similarlv make and break singly induction 

 (or faradic) shocks, and tetanizing shocks (with interrupter). Is 

 there anv difference from indirect stimulation with regard to the rela- 

 tive readiness or response to the different tornis o) electrical 

 stimulation ? 



|S~. I'olar stimulation of muscle. a. Stimulation at cathode 

 and anode. Slit a curari/ed sartorius from its lower end about 



5" 



