STUDIES ON THE OESTROUS CYCLE IN THE RAT

Abstract

A study of the length and character of estrual cycle was made in 2 groups of albino rats, one kept under rather constant conditions of room temperature (22[degree]C), the other out of doors during the 3 coldest winter months. The length of cycles averaged 4.8 days under room, and 8.6 days under outdoor temperatures, and varied roughly with the environmental temperature. The body temperatures of the outdoor rats varied from 31 to 38[degree]C. The results are interpreted as due to the direct effect of temperature on ovarian activity and to the lowered general metabolism of these rats, shown by the lowered body temperature and lessened activity. It is probable that in nature the estrual rhythm may vary considerably with temperature.