Gonad Grafts in the Fowl

Abstract

1. A histological examination has been made of material from 19 cases of gonad grafts in fowls, from the series of transplantation experiments performed by G. F. Finlay. 2. While some of the ovary grafts remain typically ovarian in structure, many show extensive changes due to a secondary proliferation of the sex cords and their further differentiation into tubules of a definitely spermatic type. Most of the testis grafts are either in active spermatogenesis or are composed of an intimate mixture of active and atrophic tubules; in 2 cases they consist of atrophic tubules only. 3. It is suggested that the formation of atrophic tubules may be due, apart from environmental conditions, to mechanical pressure. 4. Islets of typical "luteal" cells are present in the interstices between the inactive tubules in the testis grafts, and are not associated with a henny type of plumage. In ovarian grafts "luteal" tissue is found in the thecæ of the follicles, as in the normal ovary, and also in the region of undifferentiated sex cord tissue and tubules. 5. It has not been possible exactly to determine the origin of the new proliferation of the sex cords in the ovarian grafts. It would appear that they may be derived from the germinal epithelium and also from the intra-ovarian epithelial elements represented by the degenerating medullary cords. 6. There appears to be some time relation involved in the formation of the secondary proliferation of the sex cords in the ovarian grafts, since (with one exception) none are found in grafts made later than the fourth day after hatching. 7. Two cases of an activated right gonad in the ovariotomised female are described, of which one shows typical ovarian structure. The hypothesis is put forward that the right gonad is female fundamentally in constitution, and if it differentiated under a specific stimulus (normally characteristic of the female chick at an early stage of incubation but exceptionally reproduced at a later stage in development) an ovary would be formed.