Recherches préliminaires sur les chimères d’organs embryonnaires d’oiseaux et de mammifères en culture in vitro: (Mémoire dédié à M. le Professeur F. Baltzer, de T Université de Berne, àl’occasion de son 70e anniversaire)
Authors: Wolff Étienne , Weniger J.-P. 
Published: April 2021

ABSTRACT
Gonads, dissected from mouse embryos of between the 13th and 16th days of gestation, were associated in vitro with embryonic gonads from ducks at the 8th to 11th day of incubation. The culture medium was the ‘standard medium’ elaborated by Et. Wolff and K. Haffen at the Laboratory of Experimental Embryology of Strasbourg. Gonads coming from these two different zoological classes will fuse together, whatever their sex, so that they form an inseparable unit, in which it is difficult to see from the exterior the limits of the two components. Histologically, the field of each partner is generally distinct, except in the intermediate region, where close connexions are formed between somatic and germinal tissues of both species. In all combinations, the connective tissues are always intermingled. In the association of duck testis with mouse testis, connective tissue cells of the mouse slip under the germinal epithelium of the duck and spread far from their initial area (Plate 1, fig. B). Mouse seminal tubules communicate with duck seminal tubules, forming chimeric structures (Plate 1, figs. A and C). Sertoli cells of both species collaborate in the formation of the wall of the tubules, in which mouse spermatogonia are to be seen alongside duck spermatogonia (Plate l,fig. D). In the association of duck ovary with mouse ovary, somatic and germinal cells show a tendency to be intermingled (Plate 1, fig. E; Plate 2, fig. G) in the intermediate zone; the cortex of the duck has a tendency to surround the whole gonad of the mouse (Plate 2, fig. F). In the association of mouse ovary with duck testis, an ovarian cortex, more or less thick, is formed around the duck testes. Connective tissue cells of the gonad of the mouse migrate far from their origin under the basal membrane of this cortex (Plate 2, fig. H) and between the testicular cords of the duck. In the contact zone, somatic cells and ovocytes of the mouse are to be found in the testicular tubules of the duck (Plate 2, figs. H and I). In the case of an association between duck ovary and mouse testis, somatic tissues are mixed in the neighbourhood of the contact zone. Pflüger’s cords of the duck open into the testicular tubules of the mouse, so that duck ovogonia are to be seen close beside mouse spermatogonia (Plate 2, figs. J and K). These results give evidence that there is no incompatibility between embryonic gonads of two different zoological classes when they are directly associated in a culture medium in vitro. Their tissues are able to fuse together, without any sign of repulsion. In several cases cells of both partners show, on the contrary, affinities and the ability to collaborate. How often and up to what stage of the embryonic or postnatal life such xenoplastic associations are possible is still an unsolved problem. Another problem to which the present data lead is the difference in the behaviour of xenoplastic associations in vitro and in graft experiments.