ADRENAL ORGANS 



355 



in position with the nephridial structures, though they have no other 

 relation to them. The two differ in structure and probably in func- 

 tion and are very distinct in the lower vertebrates but in amphibia 

 and amniotes they are united in a common structure, the interrenals 

 forming the cortex, the suprarenals the 

 medulla of the mammalian adrenals. 



The interrenals arise from the coelomic 

 epithelium, but it is as yet uncertain as to 

 the details, some thinking that they are con- 

 nected with the pronephros, others with the 

 mesonephric structures, while still others 

 regard them as distinct in origin. They are 

 at first either isolated clusters of cells or longer 

 bands of cells near the dorsal margin of the 

 mesentery, sometimes bilaterally symmetri- 

 cal and in the lower vertebrates in the early 

 stages extending through the length of the 

 coelom. 



Fig. 376. IiG. 377. 



Fig. 376. — A, Diagram of the phacochrome system of a just-born rabbit; B, of a 

 forty-five day girl, after Kohn. a, aorta; k, liidney; p, phacochrome bodies; r, rectum; s, 

 suprarenal; «, ureter. In A the connexion of the bodies with the medulla of the supra- 

 renal is indicated. 



Fig. 377. — Adrenal system of Scyllium, after Swale Vincent, a, axillary heart; ao, 

 aorta; i, interrenals; s, suprarenals. 



The anlage of the suprarenal bodies is in the sympathetic ganglia, 

 certain cells of which separate from the rest. Some of these retain 

 their ganglionic character through life, while others are the chro- 

 maphile or phaecchroine cells, so-called because they stain brown or 

 yellow with chromic salts. These are usually closely related to 



