PARS INTERMEDIA AND PARS TUBERALIS 



xanthosomes (or xantholeucosomes).' Removal of the pars 

 glandularis alone is not followed by such changes whereas 

 they occur in a typical fashion after the removal of the neuro- 

 intermediate lobe. Other experiments are in accord with the 

 view that the hormone causing dispersion of the melanosomes 

 is secreted by the pars intermedia, xAmong such observations 

 is that of Bayer (1930) who investigated the pituitary of a 

 frog which, among a large shipment, alone had a pallor of 

 the skin. He found a pronounced atrophy of the pars inter- 

 media due, he beheved, to the invasion of a trematode, 

 which had died subsequently. The transplantation of the 

 pars intermedia (adult frogs) into normal or hypophysecto- 

 mized tadpoles causes a marked dispersion of the melano- 

 somes persisting as long as the graft remains alive (Allen 

 1920, 1925, 1928-30, and Swingle, 1921). If suspensions of 

 the various parts of the ox-pituitary are injected into tad- 

 poles, the most marked immediate effects are caused by ex- 

 tracts of the pars intermedia; suspensions of the pars glandu- 

 laris were found to be more potent than those of the pars 

 neuralis (Smith and Smith, 1923). (Other data on the dis- 

 tribution of this hormone in the pituitary and elsewhere are 

 discussed later.) 



Although in some amphibia light may directly affect the 

 chromatophores, the melanophores of the frog (and probably 

 toad) are altered chiefly because of optic stimuli. Adaptive 

 coloration in these Anura, so far as the melanophores are 

 concerned, appears to depend upon the nervous regulation 

 of secretory activity in the pars intermedia. In support of 

 this statement several types of experiments may be described. 

 The removal of the eyes, but not spinal transection, abolishes 

 the changes in the chromatophores adapting animals to light 

 or dark backgrounds (Hogben and Slome, 1931, and others). 

 Schiirmeyer (1926) found that an injury of the floor of the 



'Hogben (1923-24); Hogben and Winton (1923); Giusti and Houssay (1924); 

 Houssay and Ungar (1924); Hogben and Slome (1931); and Zieske (1932). 



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