Twelfth Generation Research Articles

Metaplasia and metastasis of a rat tumor

We reported to this society on several previous occasions some facts regarding a tumor of the rat which we have propagated for more than two years. This tumor is now in its twelfth generation. The original tumor was of complex histological structure and has been regarded by us as consisting predominantly of a tissue of sarcomatous nature and to a less extent of irregular tubular formations resembling structures seen in certain endotheliomata. In the fifth generation of one series of transplantations, metastases were first noted in the regional lymphatic glands. In all previous generations the metastases were to the lungs and the kidneys; and in the other series this change in properties has not been observed. In the succeeding generations between the fifth and the eleventh, of the particular series mentioned, the lymphatic metastases have grown more common and more widely disseminated. Coincident with this change in properties of the tumor, a modification in the histological structure has been noted; the ...