Abstract
In 1921 one of us showed that feeding fresh anterior lobe of the hypophysis of cattle has no effect on the metamorphosis of Urodelan amphibian larvae. 1 As Smith 2 obtained precocious metamorphosis by feeding Armour's anterior lobe powder, he felt certain that this preparation is not pure anterior lobe powder, but owes its action to the presence of iodine or thyroid substance in it.
We fed anterior lobe powder to larvae of the Utah axolotl, raised from eggs in the laboratory and kept under identical conditions. A 1928 sample of Armour's commercial anterior lobe powder and anterior lobe powder prepared in our own laboratory by the method described in Article I of this series were used.
In one experiment 2 controls metamorphosed at an average body length of 58.2 mm., average age 141 days; 3 experimental fed on our own anterior lobe preparation metamorphosed at an average body length of 63.7 mm., average age 140 days; and 2 experimental fed on Armour's anterior lobe powder metamorphosed at an average body length of 65 mm., average age 135 days; one of the latter 2 animals attained the largest size before metamorphosis (68.1 mm.) among the entire 1928 material. The feeding lasted for a period of approximately 102 days. Feeding of a 1928 sample of Armour's thyroid powder, in the same kind of larvae, caused metamorphosis 14 days (at the latest) after the beginning of the experiment.
Neither our own nor Armour's preparation of anterior lobe had any effect on the metamorphosis of the salamander larvae when administered by mouth, while they proved most potent when injected intraperitoneally. Armour's preparation behaved in this respect entirely as our own preparation, and both differed from armour's thyroid powders.
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