PARS INTERMEDIA AND PARS TUBERALIS 



ever, changes in the erythrophores are regarded as being due 

 to the secretion or extract of the pars intermedia. Indeed, 

 some investigators hmit their observations to the erythro- 

 phores. 



In Giersberg's experiments (1932) the effects of the ap- 

 pHcation of pressure to the pituitary in situ as well as those 

 of pituitary destruction were investigated in Phoxinus. He 

 concluded that the distribution of pigment granules in 

 erythrophores and xanthophores was probably under the 

 control of the pituitary whereas that in the melanophores was 

 regulated by the nervous system. Pressure on the pituitary 

 was followed by a dispersion of the xanthosomes and eryth- 

 rosomes. Analogous experiments were undertaken by Col- 

 lin and Drouet (1933) who used fish in full "wedding dress"; 

 unhke Giersberg they found that pressure on the pituitary 

 caused a concentration of the erythrosomes. Zondek and 

 Krohn (1932) studied the effect of pituitary extracts on the 

 appearance of the erythrophores. They concluded that the 

 hormone** is specifically elaborated in the pars intermedia and 

 described a technique for assaying the hormone in fish about 

 7 cm. long.'' Peczenik (1933), unlike most observers who be- 

 lieve that the hormone acts directly on the erythrophores, 

 concluded that part of the hormone's effect is on spinal 

 autonomic centers. According to Zondek and Krohn, the in- 

 jection of an extract of the pars intermedia (ox) may cause 

 an increased formation of red pigment in the skin of Phoxi- 

 nus. 



Collin and Drouet (1934) as well as Stutinsky (1934) con- 

 cluded that extracts of other tissues (e.g., thyroid, ovary, 

 thymus, spleen, etc.) may also cause a dispersion of erythro- 

 somes similar to that produced by extracts of the pars inter- 

 media. They also believed that only the male is suitable for 



* They proposed the name "intermedin." 

 'The maximum adult length is 14 cm. 



[305] 



