RECIPROCAL CHORIO-ALLANTOIC TRANSPLANTS OF EMBRYONIC DUCK AND CHICK KIDNEY TISSUE

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Abstract
1. Metanephric tissue from duck and chick embryos that were approximately equivalent in development was transplanted to the chorio-allantoic membrane of the chick and duck respectively. The hosts, also, were incomparable stages of development. 2. A reciprocal relation was found to exist during the early embryonic stages only. As development progressed this relation was lost, to a large extent; prominent differences occurred in the two types of transplants. Whereas relatively slight or no reactions were observed in the duck-on-chick grafts, intense reactions appeared in the grafts of the reverse host-donor relationship. 3. The reactions appearing in the grafts were associated with the development of the species specificity factor in the donor tissue. Its appearance in the chick tissue occurred at about the fourteenth day of incubation. 4. The reactions which appeared as a result of the development of the species specificity factor were: (1) a decided retardation of the rate of incorporation of the implanted tissue; (2) possible expulsion of the transplant from the membrane; and (3) the stimulation of leucopoietic centers in the connective tissue of the surrounding host membrane. These reactions, if present in the duck-on-chick grafts, were scarcely observable because of their mildness. 5. It was demonstrated by these experiments that, although the host reacted against the transplant, which obviously instigated the reaction, it was also possible, as was shown by an analysis of the process of incorporation, for the transplant to react against the host. 6. Seemingly contradictory results were obtained in the grafts of fully differentiated, species specific tissue, in that the implants were readily incorporated into the host membrane, without provoking a reaction. Although no evidence was offered, an explanation of these unusual results was suggested which was based on the theory of Loeb (1930) that the reaction against a transplant is dependent, to a large measure, on the active metabolism of the transplanted tissue.