Abstract
Spaul 1 reported that injections of anterior lobe substance induced metamorphosis in thyroidectomized axolotls. According to our work, however, the effects of the hormones are quite different and anterior lobe cannot replace the thyroid hormone.
To test our claim 6 larvae of the Utah axolotle were most carefully thyroidectomized. As complete thyroidectomy of salamander larvae is very difficult and regeneration of remnants not visible under the dissecting microscope takes place frequently, the injections of an anterior lobe extract prepared in our laboratory, as described in Article 1 of this series, were started in 4 of the thyroidectomized larvae immediately (one day) after the operation. Two normal control larvae of the same stage and approximately same size were injected at the same time with the same sample of anterior lobe powder as the experimentals. Both controls metamorphosed after the sixth injection, 11 days after the first injection. None of the experimentals showed even a sign of metamorphosis after the ninth injection, fifteen days after the first injection. The injections were stopped after the ninth injection; 51 days after the first injection, the experimentals are still completely larval.
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