Abstract
Summary
1. Normal young albino rats had a temperature of 36.4°-37.2°C. in the cold, in a warm room 37.7°-38.3°C. 2. Surviving hypophysectomized rats maintained their body temperature for 16 days in a cold room (2°-4.5°C.) at 35°-36.15°C. From the 20th to 34th days the temperature fell approximately 1.3°-2.7°C. 3. The thyroid glands of normal animals in the cold showed activity as previously described by other investigators. Those in the warm room had a lower epithelium and fewer absorption vacuoles. 4. The glands of hypophysectomized rats 38 days in the heat showed atrophy. Similar animals placed in the cold room 34 days showed signs of atrophy in the central part of the gland but absorption of colloid was indicated in the peripheral vesicles by the high epithelium, loss of colloid in the smaller vesicles, and many absorption vacuoles in the peripheral colloid of the larger vesicles. 5. The drop in body temperature of the hypophysectomized rats after 16 days in the cold as well as the histological picture of the thyroid gland indicates that cold in the absence of the anterior lobe of the pituitary is not an adequate stimulus to maintain either body temperature or a histological picture of the thyroid gland comparable to that of a normal rat.
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