SKIN TRANSPLANTATION IN FROG TADPOLES 383 



decided to place skin transplants over artificial eyes on the back 

 of the animal. The mechanical conditions of such grafts would be 

 like those over functional eyes. But the possibility of any in- 

 fluence of the visual function upon the grafts would be completely 

 removed. If the beha^^or of such grafts should be the same as 

 that of grafts over normal eyes, then the explanation that curva- 

 ture causes absorption would be substantiated. 



3. Grafts over artificial eyes, series LBE and DBE 



An incision surrounding a square of integument was made in 

 the same way as in series LB. The artificial eyes consisted of 

 hemispheres of glass or celloidin with radii equal to or slightly 

 longer than the radius of the eyeball. The hemispheres were 

 placed on the square of skin w^ith their flat surfaces down, and 

 were covered by the graft of tail or back skin. The orientation 

 was varied and some of the animals were kept in darkness. 



As is shown in tables 5 and 6, fourteen out of fifteen tail-skin 

 grafts showed absorption. The amount of illumination made no 

 difference in the result. The average number of days following 

 which absorption began was four. The grafts placed over the 

 largest hemispheres, in which the elevation of the tissue was 

 greatest, began to be absorbed earlier than the others, sometimes 

 during the first and second days. In every case the amount of 

 absorption is recorded as total, because the 'eye' came out as 

 soon as the absorbed area became large enough to permit its 

 passage. Whether the material was glass or celloidin caused no 

 variation in the process. It should be noted that infection or 

 injury of the graft was not the cause of the absorption. All 

 grafts which showed any signs of infection were discarded and 

 their records excluded from the table. After the hemispheres 

 had been freed, the transplants settled down flat and soon after- 

 ward began to proliferate new tissue, exhibiting the same charac- 

 teristics of growth as seen in the previous series. On the other 

 hand, not one of the back-skin grafts was absorbed and none 

 proliferated. All of the nine cases had similar histories, as far as 

 their behavior was concerned. Following the short healing period 

 during which complete union was established, they entered the 



THE JOURNAL OP EXPERIMENTAL ZOOLOGY, VOL. 35, NO. 4 



