MUSCLE-NERVE. 



trodes from the secondary of an inductorium arranged for single 

 make-and-break stimuli. Close the galvanometer key. There will, 

 probably, be more or less deflection of the needle due to the demar- 

 cation current of the muscle which was injured in preparation. 

 With the galvanometer key closed, stimulate the nerve with a 

 single make or break shock. The muscle will respond with a 

 single twitch. Is there any movement of the galvanometer needle ? 

 If so, how much and in what direction ? 



7. Action Current of Frog's Heart. Pith a frog. Remove 

 the heart, being careful to include the sinus venosus. The heart 

 will, probably, continue its pulsation 



after its removal from the body of 

 the frog. Place the heart on non- 

 polarizable electrodes, connected 

 with the capillary electrometer. 

 With a low power of the microscope, 

 watch for movements of the menis- 

 cus of the mercury in the capillary 

 tube. How many movements can 

 you make out ? How do they corre- 

 spond with the beating of the heart ? 



8. Paradoxical Contraction. 

 Pith a frog. Make a sciatic-gas- 

 trocnemius preparation, tracing out 

 and cutting the anterior tibial branch 

 of the nerve. Stimulate the cut 

 branch (see Fig. 16). The muscle 

 will contract. 



9. Muscle Tone of Rabbit's Gastrocnemius. Demonstra- 

 tion. Narcotize a fair-sized rabbit with a hypodermic injection of 

 one grain of morphine sulphate. Complete anaesthesia with ether. 

 Tie rabbit, belly down, on the rabbit board, with the hind limbs 

 well stretched out. Make a longitudinal incision through the skin 

 and separate the dorso-lateral thigh muscles. The large shiny 

 white sciatic nerve will be exposed, deep in the wound. Tie a 



[37] 



FIG. 16. Paradoxical Contrac- 

 tion. ' J, Sciatic nerve ; /, branch 

 to peroneus muscle ; e, electrodes ; 

 , gastrocnemius muscle. 



