THE PITUITARY BODY 



the pigmentary changes resulting from the removal of the 

 pars buccalis or of some of its parts from both larval and 

 adult amphibia/ as well as studies of the effects of extracts of 

 different divisions of the pars buccalis, justify the conclusion 

 that the pigmentary change is the result of the removal of the 

 pars intermedia. The important alteration appears to be due 

 to a "contraction" of the melanophores, i.e., the granules of 

 melanin instead of being diffusely distributed in the pigment- 

 cell and its processes are clumped together in the central part 

 of the cell.^ As a result, the skin appears to contain less black 

 pigment — the degree of the change depending upon the 

 number and nature of the other chromatophores. In addi- 

 tion, there is observed a marked "expansion" of the xan- 

 tholeucophores (tadpoles, frogs, and toads). In hypophysec- 

 tomized tadpoles there is also a reduction in the amount of 

 free melanin and in the number of melanophores in the epi- 

 dermis (Allen, Atwell, Smith). '^ Hogben and Slome (1931) 

 concluded that the adaptation of X. laevis (and perhaps of 

 frogs such as R. Jusciguld) to a white background could not 

 be accomplished unless the pars tuberalis was intact. The in- 

 direct control of the chromatophores by means of nerve fi- 

 bers, presumably ending in the pars intermedia, is discussed 

 in chapter ix. 



Other changes in the skin of hypophysectomized amphibia 

 have also been described. Giusti and Houssay (1921) de- 

 scribed a bronzing or blackening of the skin in hypophysec- 

 tomized toads {B. marinus) due to a hyperkeratosis. Later, 

 they found that a similar change occurred as a result of le- 

 sions of the tuber cinereum (Giusti and Houssay, 1922; 

 Houssay and Giusti, 1929). The removal of the pituitary or 



5 Tadpoles, frogs, toads, and salamanders. 



* See Sumner (1933), and Mast (1933). 



7 Allen (1916-18, 1929-30); Smith (1916, 1920-23); Atwell (1921); Hogben and 

 Winton (1923); Houssay and Ungar (1924); Puente (1927); Houssay and Giusti 

 (1929); Hogben and Slome (1931); Zieske (1932); and Adams (1933). 



[40] 



