Transplantation into foreign hosts of the kidney carcinoma of leopard frogs has been investigated by grafting the tumor in the anterior chamber of two other species belonging to the same family of frogs (green frog, bullfrog), of a species from a different family (the toad), and of animals of different classes of cold-blooded vertebrates (goldfish, alligator). In the eyes of frogs of alien species, the kidney carcinoma became established as readily as in the eye of the natural host. In toads, the proportion of successful transplantation was slightly less. No progressive growth of transplanted tumor occurred in the fish or the reptile, although in fish characteristic tumor acini persisted and a few mitoses were to be found long after implantation. In the alligator the transplants deteriorated much more rapidly. Thus the success of transplantation into alien species decreased as the relationship to the original species became more distant.
An inflammatory reaction to the tumor graft appeared in the eye of reptiles and fish, but no such reaction occurred in amphibians.
The character and rate of growth of transplants were followed by continued direct examination with the microscope and were found to be practically the same in the eye of alien species as in the original species. Nor were differences in the finer structure of the tumor observed in the several species. The neoplastic cells retained their acinar arrangement, supported by stroma which developed quite as well from the tissues of alien hosts as from those of the natural host.
It was possible to engraft the tumor in the eye of the natural host, then to transplant it into the eye of another species, and finally to retransplant it in the original species. In this way the tumor has been propagated for 443 days.
A tissue culture of the tumor has been successfully transplanted into the eye of an alien host.
Thus these results demonstrate that, among cold-blooded vertebrates, the humors and tissues of the eye have a high degree of tolerance for foreign tumor grafts.