318 



T/te Pigmentary Effector System. I. — Reaction of Frog's 



Melanophores to Pituitary Extracts. 

 By Lancelot T. Hogben, M.A., D.Sc, and Frank E. Winton, M.A. 



(Communicated by Prof. E. W. Mac-Bride, LL.D., F.R.S. Received February 2, 



1922.) 



(From the Zoological Laboratory, Imperial College of Science and Technology.) 



CONTENTS. 



PAGE 



1. Introduction 318 



2. Specificity and Localisation of a Pituitary Melanophore Stimulant 320 



3. Sensitiveness of the Melanophores to Pituitary Extracts 322 



4. Relation of the Melanophore Stimulant to the other Pituitary Autocoids 323 



5. Relation of the Melanophore Stimulant to Histamine 325 



3. Mode of Action of the Melanophore Stimulant 326 



7. Summary 328 



1. Introduction-. 



The ability of certain organisms, including notably the Mollusca and lower 

 Vertebrata, to respond to their surroundings by appropriate pigmentary 

 changes has long been familiar to biologists ; it has been recognised for more 

 than half a century that a special type of effector organs (chromatophores, 

 melanophores, etc.) are actively instrumental in producing such changes, and 

 that, in Vertebrates at least, pigmentary response is partially controlled 

 through the nerves by stimuli received from the organs of vision. During 

 the past two decades it has been shown that the reactions of the pigment 

 cells to stimuli simulate those of other effector organs, especially as regards 

 their responses to certain internal secretions. That a fuller understanding of 

 their properties might prove of service to practical aspects of physiology, as 

 well as the key to a knowledge of " colour adaptation," was realised by Lister, 

 who concludes his paper on the cutaneous pigmentary system of the Frog 

 (1858) with the following comment : " The pigmentary system also promises 

 to render good service in toxicological enquiry. Hitherto in experiments 

 performed on animals with that object attention has been directed chiefly, if 

 not exclusively, to the effects produced upon the actions of the nervous 

 centres, the nerves, and muscles. In the pigment cells we have a form of 

 tissue with entirely new functions, which, though apparently allied to the 

 most recondite processes, yet produce very obvious effects. . . . Such 

 experiments are so readily performed, and the effects produced are so 

 obviously indicated by the changes in colour of the integument, that I 



