In order to investigate the effects of high ambient temperature on the thyroid, a total of 50 rabbits (mean weight, 1,294g) reared under 7℃ were alloted to two groups. Rabbits in one group served as controls and the others, after reared under 30℃ for 16 days, were returned to the normal temperature for 16 days.
The results obtained in this work were summerized as follows:
1. The weight of the thyroid gland was decreased severely from the 2nd day and increased to normal range on the 4th day after returned to normal temperature.
2. Thyroid follicles were atrophied significantly from the 1/2 day and then enlarged gradually from the 4th day, while their colloid substance also manifested poor staining, coagulation, and disappearence, being reappeared from the 8th day.
3. Hypertrophied follicular epithelial cells showed more enlarged size, degeneratien, necrosis, and mitosis from the 1/2 day in accordance with experimental term and those changes were diminished from the 8th day.
4. Histologically thyroid manifested-hypothyroidism on the 16th day but showed mild hyperthyroidism on the 2nd day and euthyroidism from the 4th day of returned roaring.
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