THE PITUITARY BODY 



oxyphil and reserve cells. Their results therefore suggested 

 that the thyrotropic hormone is secreted by the basophil 

 cells. ^ Allen (1932) later studied the anterior pituitary of tad- 

 poles before and during metamorphosis. During metamor- 

 phosis the basophil cells were more numerous and stained 

 more deeply than before metamorphosis. By a different type 

 of evidence Allen also supported the view that the basophil 

 cells secrete the thyroid-stimulating principle. 



Coincident with metamorphosis induced by anterior pitui- 

 tary there occur histologic changes in the thyroid indicating 

 increased activity characteristic of normal metamorphosis. 

 The colloid tends to disappear or stain poorly and the acinous 

 cells appear cuboidal or columnar rather than flat; hyper- 

 plasia and cytologic changes have also been described (Uhlen- 

 huth and Schwartzbach, 1927, 1928; Ingram, 1929; Grant, 

 1931; and Clements, 1932). 



The suggestion that lack of pituitary development is re- 

 sponsible for neoteny (appearance of sexual maturity during 

 the larval stage) in some amphibia was made by Goldschmidt 

 in 1912 (see Adler, 1914). Ingram (1929) was of the opinion 

 that neoteny is the result of a hyposecretion of the thyro- 

 tropic hormone. The existence of neotenic species suggests 

 that stimulation of the thyroid by the pituitary is due to a 

 principle differing from that stimulating the gonads. 



In most of the work on thyroid stimulation in amphibia, 

 suspensions or crude extracts of the anterior pituitary have 

 been administered. Apparently the principle withstands boil- 

 ing in dilute aqueous solutions of acid (Spaul, 1930; and 

 Crew and Wiesner, 1930) or alkali (Krichesky, 1934). The 

 usefulness of dilute acetic acid solutions as extracting media 

 was discussed by Spaul. Metamorphosis induced by iodine or 

 iodine-containing compounds will not be discussed inasmuch 

 as this type of metamorphosis is said to occur after thyroidec- 



^ Also see the report of Spaul and Howes (1930) who concluded that the thyro- 

 tropic (metamorphic) hormone is elaborated by the oxyphils. 



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