Preparation

1. The frog is stunned and pithed, a procedure which destroys the brain and spinal cord.
2. The skin covering the lower half of the body is removed.
3. The urostyle is cut free and removed exposing the root of the sciatic nerve on both sides. A ligature is tied around the nerve and the nerve is cut central to the ligature.
4. The nerve is carefully dissected free of surrounding connective tissue down to the knee joint. Its path through the thigh may be more easily seen if the muscles are gently parted using the thumbnails.
5. Care must be taken not to touch the nerve with dissecting instruments or to stretch it unduly.
6. The in-situ length of the gastrocnemius muscle is measured and a ligature tied around the achilles tendon. This should be left long to facilitate attachment to the strain gauge.
7. The tendon is cut and the gastrocnemius muscle carefully dissected free up to the knee joint. The limb bones either side of the knee-joint are cut with coarse scissors allowing the muscle, nerve and knee-joint to be lifted free of the animal.