UROGENITAL ORGANS. 131 



with the groups in which they occur. Others will be found in 

 the larger manuals to which reference must be made. Only 

 one of these structures seems to demand attention here. This 

 is the suprarenal body, which derives its name from the fact 

 that in the mammals it forms a capsule-like structure on the 

 anterior end of the kidney. In the sauropsida it is in closer 

 connection with the gonads. In the amphibia (Fig. 137) it is 

 either on the ventral surface of the mesonephros (anura), or 

 upon its medial margin (urodeles). In the teleosts it is either 

 closely connected with the mesonephros, or is farther forward 

 in the region of the degenerate pronephros. In the elasmo- 

 branchs the suprarenal is replaced by two structures: (i), an 

 interrenal, a long, slender body just medial to the ureter, those 

 of the two sides being connected behind ; (2), a series of 

 adrenals, on either side closely connected with the sympathetic 

 ganglia. 



Development teaches that the suprarenals consist of two 

 portions different in origin and corresponding to the inter- and 

 adrenals of the elasmobranchs. One portion (the cortical sub- 

 stance, interrenals) arises from the mesothelium, and according 

 to recent observations, largely by a metamorphosis of the glomus 

 of the pronephros, the mesonephros possibly contributing to 

 some extent. The medullary substance (equivalent to the ad- 

 renals) is derived in part from the sympathetic nervous system, 

 and contains ganglion cells, and in part is mesenchymatous in 

 nature, this tissue arising from cells proliferated by the septum 

 transversum. 



