It is well known from experiments on animals that various living, normal tissues when transplanted to remote parts of the same individual or to other individuals may continue to grow. Cohnheim claims, as has been previously stated, that a distinction is to be drawn in this respect between the tissues of the adult and the foetus, where the genesis of tumors is concerned. This observer, in connection with Maas,[80] has found that the transplanted material (periosteum), although growing for a while, disappears at the end of five weeks, and it is asserted that fragments of tumors, when transferred, suffer a similar fate. Wile,[81] on the contrary, {111} who has experimented with reference to the fate of transplanted tissues and portions of tumors, reports that one hundred days after the transfer of periosteum the lung was found to contain several centres of ossification. He regards the latter as proceeding from the fragments of periosteum introduced into the jugular vein, and his results thus widely differ from those of Cohnheim. [Footnote 80: _Virchow's Archiv_, 1877, lxx. 161.] [Footnote 81: _The Pathogenesis of Secondary Tumors_, reprint from _Philadelphia Med. Times_, July, Aug., and Sept., 1882.] Notwithstanding the numerous experiments which have been made in various parts of the world to excite the growth of transplanted bits from tumors, most of them have terminated unsuccessfully. Although a temporary growth of fragments of tumors has taken place after transplantation, their eventual disappearance has usually occurred. Cohnheim lays stress upon this fact in connection with his theory of the origin of tumors. He considers that the fragments of tissue and tumors disappear in consequence of the inability of the foreign particles to withstand the metamorphosis of physiological tissues. If this opposition is neutralized, the existing germs of tumors become capable of development. Wile, however, found that eight weeks after the introduction of a bit of cancer into the lung of an animal the fragment had increased nearly twice in size. He also refers to the positive experiments of Newinsky,[82] who transplanted a bit of cancer from a dog to the subcutaneous tissue of another, young dog, and found, after five months, not only an ulcerating cutaneous cancer at the place of inoculation, but also a metastatic nodule of the size of a hazel-nut in an axillary lymphatic gland. [Footnote 82: _Allgem. medicinische Central-Zeitung_, 1876, lxxi. 875.]