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COMPARATIVE PHYSIOLOGY 



Normal Pigment Responses of the Common Frog 



Note. — " Pallor " implies contraction, 

 both dermal and epidermal melanophores. 



darkening " expansion of 



equally reliable and competent witnesses on such matters as 

 the effects of nerve section and stimulation, spinal transection 

 and extirpation of sympathetic ganglia. After the researches 

 of Oliver and Schafer (1895) into the physiological effects of 

 adrenalin a new horizon appeared. Three years later Corona 

 and Moroni noticed the effect of adrenalin in producing 

 melanophore contraction in frogs. This observation was 

 extended by Lieben's researches (1906). But though the 

 action of adrenalin in promoting melanophore contraction 

 later suggested to several continental workers, notably Fuchs, 

 the possible alternative that endocrine factors intervene in 

 the control of pigmentary responses, it was only when the 

 action of pituitary extract was tested that it became possible 

 to envisage a second endocrine system capable of inducing 

 melanophore expansion. 



This line of attack was suggested by the researches of 

 Adler (19 14), Allen (19 17), and Smith (19 16), who developed 

 the technique of hypophysectomy in Anuran larvae and called 

 attention to the condition of extreme pallor which supervenes 

 in consequence of ablation of the pituitary rudiment. They 

 did not, however, appreciate clearly the effector character of 

 the pigmentary change, which was first pointed out by Allen 



