CONDITIONS GOVERNING THE GROWTH OF DISPLACED NORMAL TISSUE

We are unwilling to draw any very definite conclusions from the experiments, partly because they show a survival of implanted skin of so much shorter duration than that which seems to occur in the case of spontaneous implantation cysts, and partly because the method of reëxposing the submerged grafts is rather a crude way of testing their vitality. Nevertheless, the following points seem clear: 1. The repeated transplantation of a piece of skin from one animal to another confers no exceptional power of growth upon that skin. 2. The repeated implantation of skin into one animal decreases, if anything, its receptivity for such grafts. 3. The burial of skin in the interior of the body causes, after a time, a change in the skin of such a nature that it cannot resume its normal function as an external covering tissue, even when its circulation \ is well maintained and it is buried in the body of the same animal. The experiments do not determine how long the cells of the skin actually remain alive, and indeed it is conceivable that the mere maceration of the protective horny layer puts the skin, when reëxposed, into the position of a moist tissue, such as the intestinal mucosa, so that it readily dries up and succumbs. Nor do the experiments throw any light upon the possible existence of cytolytic substances in the circulating fluids, although, naturally, the idea of such an action has always been present in our minds in observing the gradual loss of vitality in the transplanted tissues.