The Pigmentary Mffieotgr System. 



319 



venture to recommend this method of investigation to those who are occupied 

 in studying the action of poisons. . . ." 



A considerable literature, which has been reviewed too thoroughly and 

 recently to merit an extensive epitome here, bears witness to the intricacy of 

 the mechanism which underlies pigmental response in Fishes, Amphibia, and 

 Reptiles ; and very little work has been done on Molluscs in this connection. 

 It can be safely asserted that as many distinct types of chromatophores are 

 already known as there are different sorts of other effector organs whose 

 properties have been studied. Hence it is obvious that, apart from the intrinsic 

 interest presented by the phenomenon of colour change, a study of the pro- 

 perties of this series of effectors invites consideration in relation to a fuller 

 understanding of the role played respectively by the character of the tissue 

 and the nature of its nerve supply in the local action of drugs. The research, 

 of which this preliminary communication contains an initial account, of the 

 response of Amphibian melanophores to pituitary extracts, has been 

 approached with both these objectives in view. For present purposes it will 

 suffice to recapitulate briefly what has already been achieved in relation to 

 the endocrine factors in pigmental response. 



Earlier workers on the pigment effector mechanism concentrated their 

 attention on the nervous control. Corona, however, showed as early as 1898 

 that a glandular extract could induce pigmental changes in the frog when he 

 brought about contraction of the pigment cells with adrenalin. Lieben 

 (1906) confirmed this conclusion, and a similar reaction of pigment cells to 

 adrenalin has been demonstrated in other Amphibia and in Fishes by various 

 workers. Contraction of the melanophores of frog tadpoles was found to 

 follow pineal administration by McCurd and F. Allen (1917), whose results 

 have been since confirmed by Huxley and Hogben (1921). The latter have 

 also shown that melanophore expansion follows pituitary feeding in sala- 

 mander larvae, an observation which accords with the condition pjU- general- 

 melanophore contraction seen to follow pituitary extirpation by^!^*(¥§T6), 

 Smith (1917), Atwell (1919), and Swingle's (1921) experiments ^gp^iftgiq^ 

 pituitaries, published while these experiments were in pr'«gregj. These 

 workers experimented on Amphibia ; Spaeth (1917), on the otheri*ajJ^oiA13fB'? 

 that the melanophores of isolated scales in the Teleost fish Funchdus 

 contract in response to both pituitary and adrenal preparations. 



Whatever may be true in the case of Fishes, this is certainly not the mode 

 of response among Amphibia, as the present experiments are intended to 

 indicate. Pituitary extracts injected into the frog produce a visible 

 darkening, with complete and extreme expansion of the melanophores. 

 The results recorded show that this is a specific reaction of extracts of 



