鳥類

These studies have been carried out to test the effects of oestrogen on the development of male reproductive organs in the chick. The F_1 offspring from female Barred Plymouth Rocks×male Rhode Island Reds was used in these experiments as material birds. Sexes of F_1individuals may be discriminated at about 14 days of incubation owlng to the sex-linkage of plumage color, that is, male embryos have creamy white spot of down color on the head while female ones have none. "Ovahormone Benzoate" (Oestradiol Benzoate ; 50,000Ⅰ.U. in 1 c.c.) was used to be injected, as oestrogen. These experiments are divided into two parts according to both the time and the object of hormone injection. The first part of experiments was performed by the hormone injection (30～10,000Ⅰ.U.)into the eggs at the albumen portion near blastoderm through a hole made in the shell, the injections were made on about four or five days of incubation ; and the second part of experiments was performed by single intramuscular injection (10,000-500,000 Ⅰ.U.) in the breast of the female fowls, which were expected to lay everyday, and the injection was carried out at about 36 hours before the egg laylng, which was expected. The eggs which were laid during four days after the injection, were all put into an incubator and incubated until nineteenth day. All of male embryos in these experiments were examined under a binocular dissecting microscope to observe changes of development in the reproductive glands, Mullerian and Wolffian ducts, or any others. In a large number of cases, these tissues were examined histologically, and found that they had undergone certain changes. The results of b oth experiments (the doses of Oestradiol Benzoate are 2,000-10,000 Ⅰ.U. in an egg and 50,000-500,000 I.U.in a female fowl) resemble to each other. They may be summarized as follows: The left testis of the genetic male is markedly altered in form and struture, appearing most often as a nattened ovary-like body, having the tissues of ovarian cortex in the periphery of the testicular tissues. The development of Mullerian duct is observed. The effects on the phallus is not visible in the macroscopic observations. According to the increase of hormone doses, dark test is caused by an accumulation of melanin pigments is often seen in treated testes. In the case of intramuscular injection into the female fowl, the ratio female sex to male of survived embryos at the time of dissectomy is 68 percents and statistically highly slgnificant.