Pithing

PITHING

  • It is the manual destruction of the brain and spinal cord at spinomedullary junction to make the frog unconscious to perform various Physiological experiments.
  • Hold the frog with the left hand and bend the head down by gentle press with the index finger.
  • Insert the sharp pithing needle into the depression in the occipito-vertebral junction.
  • Push the needle forward into the skull cavity and destroy the brain by rotary movement of the needle, then turn towards backward into the vertebral column to destroy the spinal cord .
  • Pithed frog shows complete paralysis of the limbs and absence of voluntary movements like jumping or crawling.
  • Prick the skin of the limb with a needle and observe no withdrawal/ flexor reflex response.

Procedure

  • Keep the pithed frog on its back on the dissection board.
  • Cut the skin and abdominal muscles upto sternum and expose the abdominal viscera.
  • Remove the liver, stomach, intestine and kidneys without touching the under lying sciatic nerve trunk emerging from the vertebral column passing to the hind limbs.
  • Hold the vertebral column with a piece of cotton cloth and strip the skin off the legs with the help of another piece of cloth .
  • Cut the vertebral column above the origin of the sciatic nerve.
  • Discard the anterior portion of frog’s body. Separate the urostyle from the surrounding muscle and cut away its attachment with pelvic girdle. With the help of a bone cutter , longitudinally split the vertebral column into two equal halves .
  • Cut the pelvic girdle carefully into two equal halves with a bone cutter . Preserve one of these legs in Frog Ringer’s solution.
  • By holding the piece of vertebral column with forceps, isolate the sciatic nerve upto pelvic girdle.
  • Observe the location of the triceps femoris, iliofibula, semimembranosus and small pyri­formis muscles on the dorsal aspect of the thigh.
  • Make a small incision between the iliofibula and semimembranosus and carefully separate the muscles along the intermuscular groove and expose the sciatic nerve.
Last modified: Friday, 3 June 2011, 8:37 AM