388 WILLIAM H. COLE 



changes which take place in tail-skin grafts are of two kinds: 

 1) those concerned with the adjustment process when the grafts 

 are over eyes, and 2) those concerned with proliferation. None 

 of these changes affect the characteristic appearance of tail skin. 

 The new tissue formed by the grafts is similar in all respects to 

 tail skin. Many of the outgrowths even possessed the shape 

 of a tail and were described as miniature tail tips. The charac- 

 teristics of the pigment pattern and the translucency of tail 

 skin were preserved in the old tissue and reproduced in the new. 

 One hundred and thirty-six transplants of tail skin on various 

 regions of the back gave uniform results in this respect. Not a 

 single graft failed to preserve its individuality. The periods of 

 observation varied from two to eight months, the average being 

 six. Since the epidermal cells are constantly being cast off and 

 regenerated and since the tail skin is mostly epidermis, it is safe 

 to say that nearly all of the tissue in an old graft, say six months 

 after the operation, has been formed since the graft was placed. 



If there is any chemical action of the surrounding skin, or of 

 the tissue beneath, or of the blood and lymph, which tends to 

 change the visible characteristics of the graft, then it is evident 

 that such action is not effective. A more likely assumption is 

 that no such tendency exists, but that the cells of the grafts are 

 self-differentiating, and, if provided with nourishment, reproduce 

 their kind. It is immaterial to such tissue whether the proper 

 nourishment comes through the blood vessels of the back or of 

 the tail. In other words, the mechanism, perhaps the result of 

 a specific chemical group in the protoplasm, resides in the cells 

 themselves, and is not dependent upon any interaction with 

 other mechanisms outside the cells. 



Integument from one location on the back grafted into a new 

 position on the back likewise remains unchanged. All of the 

 cases in which back skin was placed over the eye resulted in the 

 graft's becoming indistinguishable from the surrounding skin. 

 Figure 17 shows such a graft three months after the operation. 

 The line of union is marked by a band in which the melanophores 

 are more numerous than elsewhere. This condition disappeared 

 after four months. Grafts placed on other parts of the back 



