Abstract
Growth pattern of the genitalia of the heifers of Japanese Black breed was investigated from birth to puberty. Results obtained in this study are as follows; 1. All heifers whose body weight reached 257-260 kg, had maturated sexually. At puberty, their uterine and cervical weights distributed 78. 0-139. 0 g and 22. 0-85. 0 g respectively. Uterine weights at puberty were about thirty times as heavy as those of neonatal heifer, and the outer di-ameters of uterine horn were about 2 cm. All heifers in this study needed at least 300 days for reach-ing their puberty. 2. At the puberty, the paired ovarian weights distributed from 4.9 to 10. 3 g, being 2-3 times larger than those of neonatal heifers. 3. At the puberty, the paired oviductal weights were about 2 g, and the oviductal lengths became about 20 cm. These values were about two fold of those found in neonatal heifers. 4. The body weight of the heifers showed continual increase after puberty, while there were a little increase in the uterine and cervical weight, and no growth of the oviduct either in weight or length.
