SKIN TRANSPLANTATION IN FROG TADPOLES 371 



will disappear. But if wastage does not exceed replacement, the 

 transplant will continue to exist. In many of the tail-skin 

 grafts placed over the eye, there was a local disappearance of 

 tissue; that is to say, in a certain area of the graft, the location 

 varjdng in individual cases, wastage predominated over the for- 

 mation of new cells. The result was the disappearance of tissue 

 in that area. The word 'absorption,' as used in this paper, is 

 defined as the disappearance of tissue in a small part of the graft, 

 without any intimation as to the method of such disappearance. 

 The word 'adjustment,' because of its broader meaning, has been 

 selected to designate the period in which absorption takes place. 

 During the adjustment period, a majority of the grafts, thirty- 

 seven out of fifty-five, showed absorption in varying amounts — a 

 visible proof that some kind of adjustment in the grafts was oc- 

 curring. Although the other eighteen grafts did not show this 

 sign, it is believed that they also passed through an adjusting 

 process. The reasons for the non-appearance of absorption in 

 those cases, as will be described later, are probably correlated 

 with a firmer state of union between graft and host, or thicker 

 tissue of the graft. 



The beginning of the absorption is seen first in those transplants 

 which have one edge unattached. The free edge shrinks back 

 from the incision, causing the contour of the edge to become con- 

 vex to the center of the graft (figs. 2, 6, and 18). In symmetri- 

 cally placed grafts, i.e., where the eye is beneath the center of the 

 graft, the apex of the absorbed area is directed toward the eye- 

 ball, no matter which edge was free in the beginning. Absorp- 

 tion continues until the eye is partly or fully exposed to view 

 (figs. 3, 4). The process is then checked, no further absorption 

 taking place. The time at which evidence of absorption appears 

 depends upon the amount of free edge in the beginning. Trans- 

 plants LN 18 and 75, for example, whose ventral edges were 

 unattached, began to be absorbed during the third daj^ after the 

 operation, and on the tenth day the eyes were entirely exposed. 

 When the length of the free edge is small or when only a corner 

 of the graft is free, the absorption process is delayed. LN 60, 

 with its anterior ventral corner free, illustrates such a condition. 



