SUPKAEENAL BODIES IN FISHES. 53 



extend nearly to the hinder end of the kidney in company with the interrenal (PI. IX. 

 figs. 2 & 4 ; PL X. figs. 5 & 7, s.r.). In other cases (PI. IX. figs. 1 & 3 ; PI. X. 

 fig. 6, s.r.) they cannot be traced very far behind the anterior extremity of the inter- 

 renal. AVhen the segmentally arranged bodies extend very far back they have a great 

 tendency to get less and less distinct and more fragmentary in appearance. 



Their relation to the sympathetic is made evident in a general way by ordinary care 

 in dissection, but the precise details of this relationship are not at all easy to make 

 out. Chevrel has, however, described this part of the subject with such care that little 

 need be said ; but as very little besides his work has ever been done upon this subject, 

 it may be as well to call attention to some points. It is a great mistake to suppose 

 that the sympathetic ganglia are all, or indeed mostly, wrapped up in the same sheath 

 as the segmental suprarenal bodies. This is undoubtedly true in many cases, perhaps 

 in all, of the first pair, but it is not nea,rly so common with the posterior ones. Indeed, 

 without in any way questioning the value of Balfour's developmental researches, I am 

 inclined to think that the connection between the sympathetic nervous system and 

 these bodies has been overstated. They are intimately involved in the sympathetic 

 plexuses, and often have tiny ganglia very close to them ; but in the adult, at any rate, 

 whatever their developmental relations may be, it can, in my opinion, not be truly said 

 that they are an integral part of the sympathetic nervous system. 



The Interrenal Body. — This body, as we have seen, was the structure to which the 

 name " suprarenal " was first applied. After the discovery of the " paired suprarenals " 

 of Leydig, a new name was required for the old body. This was supplied by Balfour, 

 who called it " interrenal." 



The interrenal body is an " ochre-yellow " rod-shaped structure, paired in the Rays, 

 unpaired in the Sharks, lying usually in the region of the posterior part of the kidney, 

 but sometimes extending as far forward as its anterior extremity (Pis. IX. & X. 

 figs. 1-7, i.r.). It bears a striking resemblance in its colour, general appearance, and 

 relations to the kidney, to the suprarenals of Amphibia and Reptilia. 



The unpaired interrenal of the Dog-fishes (PI. IX. figs. 2, 3, & 4 ; PL X. fig. 5, i.r.) 

 lies between the inferior surface of the dorsal aorta and the superior surface of the 

 unpaired caudal vein, or, as Chevrel prefers to call it, the " interrenal " vein. 



The paired interrenal of the Skates (PL X. figs. 6 & 7, i.r.) lies on the median 

 side of the ureter and on a superior level, so that it often lies on the dorso-internal 

 edge of each kidney adjoining the middle line. 



In addition to this one often finds slight streaks or dots of the same characteristic 

 yellow colour in other parts of the kidney 1 . 



1 This may be compared on the one hand with the multiple suprarenals of the Sturgeon, aud on the other 

 with the frequency of " accessory " suprarenals in Teleosts and in Mammals. The accessory bodies in Mammals 

 are said to consist of cortex only, and it may be as well to note here that my investigations lead me to 

 conclude that interrenal, suprarenals in Teleosts and Ganoids, and cortex in Mammals are all strictly homo- 

 logous with one another. 



