変態促進時の外形発生
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概要
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It is a well-known fact that the administration of thyroxin or its derivatives causes acceleration of metamorphosis in amphibia. However, very few researches have ever been done on the relationship existing between various external organs in accelerated metamorphosis. In an effort to pursue correlation existing between the external organs of the tadpole from the viewpoint of experimental embryology, the author performed three experiments, using iod-casein and brom-casein. The findings of the investigations are summarized as follows: (1) Both iod-casein and brom-casein pronouncedly accelerated the metamorphosis in Bufo vulgaris; the action of brom-casein was milder than that of iod-casein, and marked normalization of the process of the change of shape was observed after administration of the former. (2) The correlation between the external organs was observable only in terms of the phenomenon specific to the respective organ. (3) Development of the external form in accelerated metamorphosis did not follow normal process but was attended with abnormal disharmony. Acceleration of metamorphosis was not possible without causing disharmony in the external form. (4) It is presumed that disharmony in the external form would have been caused by a set of three groups of phenomenon that has different pattern of reaction, and subsequently by the secondary change. (5) It was proved experimentally that metamorphosis consisted of the following three sets of phenomenon as classified according to the difference in the pattern of reaction: 1. Retrogression of the embryonic organs,・. Development of the adult organs, and 3. Transition from the embryonic to the adult organs. (6) The tail, the month and the anal region have manifested changes attributable to more than two different patterns of reaction. Shortening of legs, enlargement of the perforations for the development of fore-legs, and the change similar to dropsy are some of the anomalies observed in the present experiments.(7) The simple method by unaided eyes for evaluation of the effect of thyroxin or its derivatives would be to use the development of fore-legs as a standard. For determination of the effect at the earlier stage of development, the use of the changes of the mouth and the tail-fin as standards would be most appropriate. (The present study has been conducted under the guidance of the late professor Shigetake Suzuki, M.D.)
- 千葉大学の論文