14 COLOR CHANGES IN ANIMALS 



as " pituitrin " (Parke, Davis & Co.) and " infundin " 

 (Burroughs, Wellcome & Co.) also brought on darkening 

 in pale pituitaryless dogfishes. The melanophores in 

 isolated pieces of dogfish skin reacted to these various 

 solutions in the same way as did the color-cells in the 

 whole fish. From these and other results Lundstrom 

 and Bard concluded that the darkening of Mustelus was 

 due to the action of a substance from the posterior lobe 

 of the pituitary gland in dispersing the melanophore 

 pigment which under unstimulated conditions was con- 

 centrated in the color cells. Thus these authors gave 

 a very adequate account of the darkening of Mustelus, 

 but passed over its pale phase with only slight con- 

 sideration. 



Two years later Parker and Porter (1934) repeated 

 the essential parts of Lundstrom and Bard's work and 

 obtained confirmatory results. They observed further 

 that when the defibrinated blood from a dark dogfish 

 was injected into a pale one, a dark area resulted show- 

 ing that the blood, as might have been expected, carried 

 a neurohumor that induced a dispersion of the melano- 

 phore pigment. (Incidentally it may be remarked that 

 the defibrinated blood from a pale dogfish when injected 

 into a dark one had no effect upon the tint of the re- 

 cipient.) These observations all support the conclusion 

 that the dark phase of Mustelus is due to a dispersing 

 neurohumor produced in the pituitary gland and carried 

 from that gland by the blood to the responding color- 

 cells. 



Parker and Porter, however, went further than to 

 confirm the results of Lundstrom and Bard. They at- 

 tempted to test for blanching in Mustelus by cutting 

 its nerves. Whenever an integumentary nerve in a dark 

 dogfish was cut the area thus denervated soon blanched. 

 This was best seen in the fins. If a cut about one 



