36 PIGMENTARY GROWTH AFTER ABLATION OF 



the entire animal appears somewhat translucent. While evoked 

 to an extent by the lower dilutions, these effects are much more 

 clearly expressed with the stronger dosages. If the animals 

 be examined with the binocular at five-minute intervals, the 

 progressive alterations in the pigment cells can be followed. 

 Especially uniform and particularly well pronounced is the con- 

 traction of the deep chromatophores. This contraction is the 

 most important factor in the translucent appearance which 

 follows the administration of adrenalin. 



In adrenalin treatment the superficial melanophores are also 

 affected, those of the albino more uniformly than those of the 

 normal. In the albino these cells gradually expand and after 

 an average period of forty to forty-five minutes a very changed 

 state is evident. The picture presented is the reverse of that 

 which obtains normally. Instead of these cells for the most 

 part being in a contracted condition, they now show a state of 

 expansion. Although only a part of this cell type is completely 

 expanded, the percentage of completely expanded cells has 

 definitely increased and all exhibit a more expanded state than 

 before treatment. In the large normal animal the response of 

 these cells when a considerable amount of fluid is used (40 cc. 

 per specimen) is one of expansion. If only partly expanded, 

 the processes soon present their maximum size; if already com- 

 pletely expanded, this condition persists. With a small amount 

 of fluid (10 cc. per animal) these effects are not so pronounced 

 and, curiously, are not infrequently reversed. 



The third group of pigment cells, the xantholeucophores, also 

 respond to adrenalin. In the albino the surface layer of these 

 cells is the first to withdraw its processes, a response which 

 may or may not extend to their more deeply placed brothers. 

 Indeed, not all of these cells of the superficial stratum are af- 

 fected, for here and there are interpolated areas of uncontracted 

 cells, and a maximum contraction of all these cells has not been 

 secured in the large albino, save with a lethal dose. In the 

 normal, these cells react in a most varied manner, their reac- 

 tion, as with the epidermal melanophores, apparently depending 

 upon the amount of fluid used. With the larger amount there 



