30 ANATOMY 



stage than the interrenal organ. In the 53 mm. embryo, 

 differentiation of the lateral parts of the sympathetic ganglia 

 begins. The chromaphil cells become smaller than those which 

 are to become ganglionic cells and assume their characteristic 

 reaction with chromic acid. In the 90 mm. embryo the 

 chromaphil organs have assumed their definitive forms. In 

 subsequent development, modification of the segmentally 

 arranged chromaphil masses occurs, some disappearing, others 

 undergoing fusion. There is a marked variety in the final 

 adult arrangement in the different genera. 



Amphibia. The development of the adrenals in amphibia 

 has been described by Brauer 80 for Hypogeophis. As in the 

 Elasmobranchs, the interrenal first appears as segmentally 

 paired proliferations of the coelomic epithelium which extend 

 from the pronephros to the cloaca. The chromaphil bodies 

 develop as in the Elasmobranchs but shift and take up their 

 position in intimate contact with the interrenal bodies. In 

 the posterior paired region, they lie on the medial face of the 

 interrenal. Elsewhere they lie dorsal or lateral or even sur- 

 rounding the interrenal. 



Bird. The development of the adrenal in the bird has been 

 described by Soulie. 581 The cortical portion of the gland 

 arises next to the anterior and dorsal part of the germinal 

 epithelium, posterior to the pronephros. At the 96th hour 

 of incubation in the hen's egg, and continuing for 4 or 5 hours, 

 groups of cells bud off into the underlying mesenchyme lying 

 between the mesonephros and aorta. These cells, arranged in 

 the form of epithelial cords increase in number by cell division 

 filling the entire space above and medial to the mesonephros. 

 The chromaphil system of the adrenal begins to form at about 

 the eighth day with the migration of sympathetic ganglion 

 cells into the adrenal to occupy their permanent position as the 

 adrenal medulla. 288 - 616 



Mammals. In man, the first development of the cortical 

 system is noted at the beginning of the fourth week. At 



