A Method for Inducing Limb Regeneration in Adult Anura

It has been demonstrated by Barfurth 1 and confirmed by subsequent investigators that frogs apparently lose their ability to regenerate limbs during the tadpole stage. On the other hand, a few adult frogs 2 and toads 3 have been observed with very definite indications of limb regeneration. These few cases of regeneration in adults are rare. Usually the stumps heal without regenerating.

A method of inducing limb regeneration in tadpoles too old to regenerate, after simple amputation, has been described by Polejaiev. 4 His method involves injury to the stump by cutting. Since Tubularia does not regenerate unless a cut surface is maintained where exchanges occur between tissue and environment 5 and since urodele limbs fail to regenerate when the amputation surface is covered by epidermis, 6 the following experiment was performed. The normal irritation following amputation was prolonged in Anura by baths in a saturated sodium chloride solution.

Parts of limbs were removed from Rana clamitans varying in stage from a few weeks past metamorphosis to full-grown. Twenty-two amputations were made between elbow and wrist or through the hand. All frogs were kept in water. Experimental animals were bathed in saturated sodium chloride solution twice daily for several minutes. The treatments continued for from 1 to 8 weeks with different animals. Fifteen control animals were not treated with salt.

The effects of the treatment were quite pronounced. The stump reddened, the color persisting for several hours, in some cases until the next treatment. The wounds of some of the animals bled during the salt treatments of the first 2 days; all remained open longer than those of the controls.