ADRENAL BODIES 495 



rate in most cases, be traced in the adult. The interrenals are of 

 varied size and of a whitish or yellowish colour: they occur, enclosed 

 in fibrous capsules, sometimes on the dorsal and sometimes on the 

 ventral surface of the kidney, usually at its middle or posterior 

 third, more or less embedded in its substance. They are usually 

 paired, but rarely symmetrical on either side. 



Amongst Ganoids, the suprarenals of Sturgeons are situated 

 on the median side of the cardinal veins and on the revehent veins 

 of the mesonephros : like the interrenals, they show many points 

 of similarity to the corresponding organs in Teleosts. 



Amongst Dipnoans, the suprarenals of Protopterus are closely 

 related to the intercostal arteries all along the trunk-region, and 

 have a paired and segmental arrangement. On the anterior part 

 of the cardinal and postcaval vein chromaffin cells also occur. 



In Amphibians, the interrenal and suprarenal organs become 

 united to form a compound adrenal body. In the Myctodera, the 

 main mass of the adrenal lies on the inner border of the kidney, 

 from which it is plainly distinguishable by its yellow colour. It 

 forms a band consisting of irregular lobes extending straight 

 backwards all along the mesonephros, being most strongly 

 developed at the middle part of the latter. Here, again, it is 

 intimately related as regards position with the revehent renal 

 veins, and often also with the postcaval and cardinal. In Anurans, 

 the adrenal is usually situated on the ventral side of the kidney, 

 and more or less towards its outer border, but reaching to its 

 posterior end, and appearing like an irregular, yellow streak, the 

 lobules of which follow closely the course of the revehent renal 

 veins, around which they form a branched network : frequently 

 certain of the lobules come into relation with the ventral wall of 

 the postcaval. 



In the Amniota, the restriction of the adrenals to more 

 definite and localised regions is carried considerably further than 

 in the Amphibia. They consist of a more uniform and circum- 

 scribed mass on either side in which both interrenal and supra- 

 renal substances are included. 



In the Sauropsida, the adrenals are met with in the form of 

 elongated yellow areas, with smooth or lobed borders, in the 

 immediate neighbourhood of the gonads. In Mammals, at a 

 certain period of development of which (especially in Man, 

 Fig. 348, B) they are relatively voluminous, the adrenals are situated 

 near the kidneys, and the name of the organ is due to this fact. 

 As in all other Vertebrates, these structures are closely related as 

 regards position to the great vascular trunks of the body-cavity. 



Although the two components are united in the adrenal of 

 Amniota, in the Sauropsida the relation of the one to the other is 

 not of the regular and characteristic kind seen in Mammals, but 

 there seems to be an irregular mingling of both elements. In 

 Mammals, on the other hand, as already mentioned, the interrenal 



