Completely cut the skin around the lower abdomen. Then cut down between the legs to free the skin around one leg from the rest of the skin, cut any attachments of the skin to the body. Holding the upper part of the frog firmly in one hand pull the skin down off of the leg. Be careful when pull the skin off around the knee as it is attached more firmly there.
Place the frog dorsal side up in the tray and make sure to keep the muscles moist with ringer solution at all times. Using a blunt (glass) probe separate the muscles of the upper thigh from the pelvis to the knee, exposing the sciatic nerve without touching it. Carefully cut free the sciatic nerve at the pelvic end and separate it from any connective tissue, muscle, or nerve branches down to the knee. Using heavy scissors cut through the femur and thigh muscle about 1 inch above the knee; make sure not to cut the nerve.
The gastrocnemius is the larger of the two muscles below the knee and is attached to the Achilles tendon. To tie a knot around the tendon, slip small tweezers under the tendon and grasp a piece of thread and pull it back through the opening made by the tweezers. Then wrap the free end of thread twice around the tweezers and pull the ends apart to make a knot around the tendon. Make a double knot by wrapping the free end around the tweezers in the opposite direction as you did the first time; pull the knot securely around the tendon. This would be a good time to measure the "resting" or normal length of the muscle. Cut the tendon below the knot, then gently pull the muscle up with the thread and cut it away from the bone. Separate the calf muscles from the bone and cut the tibiofibula bone just below the knee.
With minimal dissection the sciatic nerve and gastrocnemius muscle preparation should be completely free. Rinse and then immerse the preparation in ringer solution.
Keeping the muscle in the frog allowing the circulation to...