110 



THE DUCTLESS GLANDS 



respects between those of higher and lower vertebrates. In 

 the Anura the adrenals are golden -yellow streaks on the ventral 

 surface of the kidney, of about 15 millimetres in length in the 

 frog to about 28 millimetres in a good-sized toad. Their 

 width varies in a similar manner from 1 to about 3 millimetres. 

 But their dimensions vary very considerably according to the 

 size and development of the particular individual. 



In a good specimen the adrenals present a beautiful appear- 

 ance, forming on each side a series of irregular arcs with their 

 convexity outwards, and varying in width from place to place. 

 Their colour is a bright golden yellow, of a somewhat fatty 





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FIG. 25. Section of an adrenal body (corpuscle of Stannius) of the sturgeon 

 (Acipenser sturio). The " alveolar " arrangement is well seen, and the 

 cell outlines are distinct. 



al. w., walls of " alveoli " ; x., nuclei ; pr., granular protoplasm. 



aspect, and their surface is marbled with veins. In both frogs 

 and toads, although the body reaches nearly to the anterior end 

 of the kidney, it always ceases at a point anterior to the 

 posterior fifth of the organ. 



In the Urodela the adrenal is broken up into a series of strips 

 and islets which extend not only the whole length of the kidney, 

 but also anteriorly to that organ, as far forwards as the origin 

 of the subclavian artery. 



The microscopic structure is practically the same in Anura 

 and Urodela. The gland is seen at once to consist of two 

 distinct kinds of structure. The greater part is made up of 



