By this term is meant the removal of parts of the living tissues from their normal position, and their implantation in another situation.

This process has been frequently effected by experiment in animals; it is of occasional occurrence as a pathological phenomenon in man, and it is sometimes made use of for therapeutic purposes as a surgical operation.

The best known experiment is the transplantation of the spur of the cock to other parts of the skin or to the comb. Zahn implanted a whole foetal femur into the kidney of an adult rabbit, and found that it survived and grew there. Bert performed many experiments, in which he removed the tails of rats and implanted them on their Backs. A remarkable fact brought out in these experiments was, that if the implantation was made with inversion of the tail, so that the tip was in the back and the root projected out, yet the tail survived, and even sensation was restored, conduction occurring in the nerves in the reverse direction.

Several practical results arise from these experiments. For one thing, the larger the surface by which the transplanted piece was in contact with the living tissue, the greater the likelihood of success. Hence, small pieces of tissue and those which were completely buried in the living tissues were the most successful. In experiments with rats' tails, the latter required to be denuded of skin for some distance, so as to bring a considerable raw surface into contact with the subcutaneous tissue. Another fact was, that tissues from young animals were more successfully transplanted than those of adults. Again the transplanted piece commonly grew in its new situation, sometimes very markedly, as in the case of the cock's spur on the comb. This growth, however, was generally temporary, and in many cases was succeeded by diminution and complete absorption of the transplanted piece. If the transplanted piece, however, was so placed as to restore a lost part, then it remained permanently. Lastly, the tissues of animals of different species did not seem congenial, so that when, for instance, the tissues of rats were transplanted to birds they gave rise to severe inflammations (Oilier).

In man, transplantation sometimes occurs spontaneously. The greatest example of this is furnished in some cases of Tubal pregnancy in which, after rupture of the tube, the ovum may be transplanted to the peritoneum, acquiring adhesions there, and developing its placenta in connection with the vessels of the peritoneum. Then Tumours of the uterus or ovary (myomata and cysts) sometimes separate from their seats and acquire connections with other parts. It is probable that in these cases there is a gradual transplantation, the new connections being formed before the old are completely severed. Again, pieces of tissue are sometimes broken off, such as the appendices epiploicae in the peritoneum, or pieces of synovial membrane, cartilage or bone in joints. These may become free bodies, retaining their vitality without any vascular connections, or they may become attached in new positions.

Transplantation, as a Surgical operation, has long been practised. In plastic operations, involving the surface of the body or the buccal cavity, the transplantation is usually partial, the transplanted piece being left, at least for a time, in partial connection with its original seat. A complete transplantation is effected in skin-grafting, in which portions of the living epidermis are transplanted to the surface of granulating wounds. The granulating surface, being exceedingly vascular and composed of cells, very readily coalesces with any living structure placed on it.

Transplantation of bone is an interesting achievement of modern surgery. Macewen has succeeded, by successive transplantations, in restoring almost the whole shaft of the humerus, which had been lost by necrosis, and this surgeon has also shown that, after trephining the skull, the piece removed may be restored, and it will retain its vitality and acquire fresh connections. (See further under Affections of Bones).

Literature

Paget, Lect. on surg. path., ed. by Turner, 1870; Hunter, 1. c.; Eanvier, Le develop, du tissu osseux, 1865, and in Cornil et Ranvier, Manuel d'hist. path., 1881, i.; Kennedy, On the regeneration of nerves, Phil, trans. Royal Society, ser. B, vol. 188, 1897. Transplantation - Recklinghausen (very fully), Allg. Path., 1883; Hunter, Works by Palmer, iii., 273; Zahn, Congres period, internat. Geneve, 1877; Bert, Annal. de science nat., v., 1866; Beverdin, Gaz. d. hopit., 1870-71, Arch. gen. de Med., xix., 1872; Macewen, Phil, trans, of Royal Soc, 1881, and Annals of surgery, Oct. and Nov. 1887.