[Thyroid activity in common frogs and the heat resistance of their bodies and muscle tissue].

Thyroid activity of single individuals of the grass frog has been studied during winter hybernation (2-5 degrees) and heat acclimation (15 degrees) in relation to the heat resistance of the organism and muscle tissue at 2-5 degrees. A positive correlation has been observed between thyroid activity and the organismal heat resistance. At 15 degrees thyroid activity increases. It is the highest in females with a low initial heat resistance of the organism. It is assumed that changes in the heat resistance of the organism and muscle tissue are controlled by the thyroid gland. However, no correlation has been found between the initial (winter) level of the heat resistance of muscle tissue and the activity of thyroid.