THE PARS BUCCALIS OF THE HYPOPHYSIS 25 



There now was exhibited one of the most striking phenomena 

 presented in this work. The heretofore broadly expanded 

 xantholeucophores of the albinous graft gradually contracted 

 under the influence of its normal host. In half an hour they 

 were much reduced; in two hours they were punctate, even 

 exceeding in minuteness under this new stimulus the diminutive 

 size of the host's 'interference' cells (figs. 57 and 58). Likewise 

 the epidermal melanophores of the albinous graft gradually 

 expanded. This change from the altered physiological state of 

 these cells in the albino to the state characteristic of the normal 

 animal then persisted for the life of the host. 



A change as striking was exhibited by the heretofore con- 

 tracted xantholeucophores and expanded epidermal melano- 

 phores of the normal graft. In about the same interval the 

 xantholeucophores of the normal graft became broadly expanded 

 (figs. 57, 58), and after a somewhat longer interval the epidermal 

 melanophores assumed a punctate condition. These cells, then, 

 in this brief interval had changed from the functional state they 

 had so long experienced to the opposite condition exhibited by 

 them in the new host. 



There is, however, the possibility that this remarkable trans- 

 formation was due to the mechanical manipulation and not to 

 the influence of the host. This possibility can definitely be 

 excluded by the simple test involved in an autoplastic skin 

 graft. Identical incisions were made, the freed epidermis, how- 

 ever, instead of being transferred to a new host, was returned to 

 the position from which it for a brief interval had been removed. 

 In neither the normal nor albinous larvae did these cells suffer 

 any permanent change, but remained in the same condition 

 as the cells which had not been removed. 



Definite evidence has thus been secured which shows that 

 the altered state of these cells in the albino has been brought 

 about by the action of some substance present in the tissue 

 fluids and not by alterations in the nervous mechanism, since 

 we can conceive of no reestablishment of nervous connection in 

 such a brief interval. Further, it would seem probable that this 

 substance acts directly upon the pigment cell itself and not upon 



