90 PIGMENTARY GROWTH AFTER ABLATION OF 



can apparently initiate the process, but unless there be some 

 hypophysial secretion (and it would appear that this must be 

 formed at least in part by the interaction of the true neural 

 lobe with the epithelial component) the process apparently 

 cannot be completed. 



The adrenal cortex and medulla 



If the abdomen of a normal tadpole in the later larval stages 

 be opened and the ventral surface of the mesonephros be exam- 

 ined under the binocular, there will be seen a longitudinally 

 placed whitish-appearing cord. This cord, irregular in outline, 

 extends from a point somewhat cephalad to the kidney, over the 

 anterior four-fifths of this organ (fig. 37). This is the adrenal 

 gland. 



When such a specimen is dropped into an alcoholic solution 

 of sudan III or scarlet R, this cord takes on a reddish hue. Sub- 

 sequent treatment with potassium bichromate reveals, however, 

 that not all the cells of this column are tinted with the fat dye, 

 for with chromation, groups of browned cells surrounded by the 

 lipoid-containing cords are revealed. Similar differential stain- 

 ing of the cortex is shown by osmium vapor or when an osmic- 

 bichromate solution is used (figs. 38 to 41). If potassium bich- 

 romate alone is used, however, it can be readily seen that only 

 the centrally placed cells of this strand give the chromaffin reac- 

 tion, a reaction participated in also by certain groups of cells 

 surrounding the central intestinal artery and neighboring parts 

 of the aorta. By these staining methods we may thus clearly 

 show the two components of the adrenal gland, the medulla 

 exhibiting the chromaffin reaction and the cortex, or interrenal 

 component, characterized by its lipoid content. The arrange- 

 ment of these two components resembles with surprising accuracy 

 that of the adult as described by Stilling ('98) and Grynfeltt ('04). 



The adrenal components of a thyroidectomized tadpole do 

 not differ in any marked degree from those of the normal animal, 

 yet there appears to be an increase in the cortical or interrenal 

 t issue not entirely explained by the larger size reached by these 

 animals (table 9). 



