

UROGENITAL SYSTEM 



823 



A 



Fig. 464. 



A, The phaeochrome system of a just-born 

 rabbit. B, The same in a forty-five day girl, o, 

 aorta ; k, kidney ; p, phaeochrome bodies ; r, 

 rectum ; , suprarenal ; u, ureter. The connection 

 between the bodies and the central portion of the 

 suprarenal is shown in A, (From Kingsley after 

 Kohn.) 



The interrenals arise from the 

 epithelium of the coelom, there 

 being as yet considerable doubt as 

 to whether they are connected 

 with pro- or meso-nephros, or 

 whether they are totally distinct 

 in origin. They arise as isolated 

 clusters or bands of cells near the 

 dorsal margin of the mesentery. 

 Sometimes they are bilaterally 

 symmetrical, and in the lower 

 vertebrates may extend through- 

 out the entire length of the 

 coelom in the early stages. 



Both interrenals -and supra- 

 renals are separate in the fishes. 

 The interrenals are the more com- 

 pact of the two and lie between 

 the excretory organs of the two sides of the body. 



The suprarenal tissue forms- the medulla of the adrenals from a 

 series of tubules through which the blood from the suprarenal artery 

 circulates before it is carried away by the vein. The adrenals are closely 

 associated with the Wolffian bodies in amphibia, (Fig. 351) either 

 being attached to the inner margins (urodeles), or forming yellow stripes 

 (anura) on the ventral surface. In the reptiles they are lobulated bodies 

 near the gonads. 



It is from the medullary portion in mammals that adrenalin, some- 

 times also called epinephrin, is procured. This is an activator or hor- 

 mone, which acts directly on the muscles and causes an increase in blood 

 pressure. 



SUMMARY OF THE UROGENITAL SYSTEM. 



Fishes (Fig. 457) : 



The excretory system consists of elongated bodies situated in the 

 median dorsal part of the coelom. These bodies are composed of nephric 

 tubules that have funnel-like nephrostomes opening into the coelom. 

 The functional kidney is a mesonephros. The ovaries and testes (with 

 the exception of the teleosts) are sac-like structures that have ducts, 

 oviducts and vasa efferentia developed in connection with the primitive 

 nephridial duct, as in other groups. 



In teleosts there are no vasa efferentia or true oviducts, for the 

 posterior ends of both testes and ovaries are continued into a duct direct ; 

 the duct from the testes unites with its fellow on the opposite side to 

 empty into either a urogenital sinus or directly to the outside, and the 

 one from the ovary takes the eggs direct from the ovary before they enter 

 the coelom as in most of the higher forms. 



