THE PITUITARY AND THE THYROID 



amphibian larvae by administering implants or extracts of 

 anterior pituitary (Allen, 1920; Smith and Smith, 1922, 1923; 

 Swingle, 1922; Spaul, 1924; Uhlenhuth and Schwartzbach, 

 1928; Magdalena, 1933; and Schreiber, 1933). Spaul (1928) 

 was of the opinion that metamorphosis induced by anterior 

 pituitary differed in some respects from that induced by thy- 

 roid treatment. Witschi (1931), using T. torosus, produced 

 parabiosis between normal and hypophysectomized larvae. 

 Delayed metamorphosis occurred in both individuals; but the 

 hypophysectomized members always remained a lighter col- 

 or. According to Smith and Smith (1922) and Smith (1926) 

 the response of the Colorado axolotl is exceptional (among 

 axolotls) in that anterior-lobe extract antagonizes metamor- 

 phosis occurring normally or induced by small doses of thy- 

 roid extract. 



The metabolism of the axolotl, measured by oxygen con- 

 sumption, is increased following the injection of anterior-lobe 

 extract (Schwartzbach and Uhlenhuth, 1929). This effect is 

 prevented by thyroidectomy and can therefore be attributed 

 to thyroid stimulation. Winton and Hogben (1923) found 

 that hypophysectomy or removal of only the anterior lobe 

 lowered the rate of carbon-dioxide production of adult frogs. 

 Hypophysectomy or removal of the anterior lobe hkewise 

 markedly reduced the oxygen consumption o{ Xenopus laevis 

 (Charles, 1931). 



The thyroid-stimulating hormone appears to be specifically 

 elaborated in the anterior pituitary. The injection of ex- 

 tracts or suspensions of muscle, pars intermedia, or pars neu- 

 ralis caused neither metamorphosis nor thyroid stimulation in 

 the tadpole (Smith and Smith, 1922; and Spaul, 1925). 

 Smith and Smith (1923) found that the central part of the 

 beef anterior pituitary, often distinguishable grossly as a 

 darker area and composed chiefly of basophil and reserve 

 cells, was more effective in causing thyroid stimulation (and 

 metamorphosis) than the outer lighter portion made up of 



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