Experiments on the intracerebral implantation of embryo tissues in rats

Abstract

The experimental implantation of embryo tissues into adult or growing animals of the same species has been practised both by embryologists and by pathologists—by the former in the study of the capacity of the implanted tissues for independent growth and differentiation, and by the latter usually in the hope (which has not been realized) of shedding light on the genesis of tumours and especially of the teratomata. Fishes, amphibians, birds, and mammals have been used in these studies; and the more important of the easily accessible accounts include those of Zahn (1884), Féré (1895–1903), Birch-Hirschfeld and Garten (1899), Traina (1902), Nichol (1905), Del Conte (1907), Askanazy (1907, 1926), Petrow (1908), Tiesenhausen (1909), Shattock and co-workers (1910), Freund (1911), Dietrich (1912), Reinke (1913), Weber (1920–23), Bosaeus (1926) (who gives a complete and very useful summary of the literature up to 1926), Pichler (1933), and Nicholas (1934). In general, the results which have been obtained may be summarized briefly as follow. Embryos or parts of embryos, implanted whole or minced or pulped into adult animals of like species, may suffer any of three fates: (i) the tissues may be rapidly and completely absorbed, or (ii) they may survive, grow, and differentiate for some days or weeks, and then suffer resorption, or (iii) they may grow to considerable masses of mixed differentiated tissues which may persist for long periods, even for the lifetime of the host animal. The results vary with the species of animal, the age and degree of subdivision of the embryo tissue introduced, the site of implantation, and probably the age, health, and other personal peculiarities of the host animal. Although some workers have claimed to observe the development of tumours from the implanted tissues, none of the instances of this alleged transformation can be accepted as proved.