262 COMPARATIVE ANATOMY AND PHYSIOLOGY. 



outer surface of the kidney of a rabbit or of a man is 

 quite smooth ; this fusion affects also the inner sub- 

 stances of the lobes, and in man three, or only two, 

 tubes open directly into the pelvis of the organ. 



/"^ 



j ^S |> 



OW 



iifi 





tfpo 



M 



Fig. 109. Diagrams of the Urinary Tubules of 



A. The frog; B, tortoise; c, pigeon (after Hufnerl; D, man (after Ludsvi ?) ; I., 

 glomerulus ; n. to vn., various regions of the tubule. 



The duct that carries to the exterior the secretion 

 of the kidney is ordinarily known as the ureter ; 

 so long as the pronephros persists, the segmental 

 duct and the ureter are one and the same ; when 

 the mesonephros appears, the duct becomes divided 

 into two, the Miilleriaii duct (which has no con- 

 nection with the kidney, but forms the oviduct of the 



