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EXPERIMENTAL PHYSIOLOGY 



LV. NERVE MUSCLE PREPARATION (OPTIONAL). 



Apparatus. Put a frog in a bottle or jar, pour in a little chloro- 

 form, and cork the bottle. As soon as the frog is still, remove it 

 from the jar and, with a scalpel, sever the spinal cord just back of 

 the skull. With a wire, destroy the brain and spinal cord. Dissect 



FIG. 41. sc, sciatic nerve; g, gastrocnemius; ad, 6, etc., other muscles. 



away a hind leg; remove all the muscles except the gastrocnemius, 

 and separate this at its lower attachment. Fasten the femur strongly 

 in a clamp. With a pointed glass rod separate the sciatic nerve at 

 the upper part; do not touch it with metal instruments. Into the 

 lower end of the muscle insert a hook and connect it with a lever 

 as in Fig. 42. Connect a copper wire, insulated except at the end 

 which is to be used as an electrode, with each pole of a battery of 

 two dry cells. For convenience a key of some kind may be inserted 

 in the circuit to make and break. 



