PARS INTERMEDIA AND PARS TUBERALIS 



tration of the melanosomes (Collins and Adolph, 1926)," the 

 changes in the chromatophores of Urodela after hypophy- 

 sectomy or after the administration of pituitary tissue or ex- 

 tract are similar to those already described in Anura. How- 

 ever, the observations are fewer and not so complete. The 

 effects of hypophysectomy on the chromatophores of Urodela 

 have been described by Blacher (1927), Marx (1929), Klatt 

 (1931), and Dubowik (1933)." The effects of pituitary trans- 

 plants or extracts have been investigated by Smith and 

 Smith (1922), Burns (1930), and Noble and Richards (1932). 

 (See also chap, vii.) 



Witschi (1931) performed parabiosis experiments in newts 

 {Triturus torosus) and frogs. If a larval normal newt and a 

 larval hypophysectomized newt were united parabiotically, 

 metamorphosis, although delayed, occurred in both. How- 

 ever, the cutaneous melanosomes were always more concen- 

 trated (lighter hue) in the hypophysectomized newt. Witschi 

 also produced parabiotic union between normal and hypo- 

 physectomized frogs; after about 2 weeks, there was no 

 difference in the melanophores of a pair of such animals. 



The effects of drugs on chromatophores. — It is necessary to 

 mention only a few of the many reports describing the effects 

 or lack of effects of drugs on the chromatophores. Nearly all 

 the experiments have been performed in intact frogs. Epi- 

 nephrin causes a concentration of the melanosomes (Lieben, 

 1906, and others);'' Kobayashi (1928) found that the effect 

 of acetyl chlorine was similar. Hogben and Winton (1922) 

 tested some of the commonly used alkaloids, glucosides, and 

 amines (including barium chloride). Only nicotine or apoco- 

 deine caused dispersion of the melanosomes provided that 



"According to Hogben and Slome (1931), light has important direct effects on 

 the melanophores of Necturiis. 



"Other cutaneous changes, such as an interference with molting, may also 

 occur. 



" Dietel (1933) believed that epinephrin is not a hormonal antagonist of the 

 melanosome-dispersing hormone under normal conditions. 



[3"] 



