THE BIOLOGY OF THE FROG 



CHAP. 



Structure and Function of the Kidneys. — The kidneys 

 of the frog are oval, flattened, dark red bodies lying dorsal 

 to the peritoneum of the posterior portion of the body cavity. 



The duct of the kidney, 

 Cy Ao or ureie7', is joined at 



about the posterior third 

 or fourth of the outer 

 margin ; it then runs for 

 a short distance along 

 the dorsal surface and 

 finally becomes embedded 

 in the substance of the 

 kidney, running near the 

 margin to the anterior 

 end of that organ. The 

 ventral surface of the kid- 

 ney is flatter than the 

 dorsal and is traversed 

 longitudinally by the yel- 

 lowish adrenal body. The 

 kidneys are covered by 

 peritoneum only on the 

 ventral surface with the 

 exception of a very short 

 space where this mem- 

 brane is folded in over 

 the edges. 



The kidney may be 

 regarded as a compound, tubular gland, made up of a 

 large number of coiled uriniferous tubules. Each urinif- 

 erous tubule begins in a Malpighian body near the ven- 

 tral surface. A Malpighian body consists of two parts, 

 a knot of blood vessels, the glomerulus^ and a sur- 



FiG. 52. — Male urinogenital organs. 

 Ao, Aorta ; 67, cloaca ; Cv, postcaval 

 vein; FK, fat bodies; Ho, testes; 

 Ur, ureters opening into the cloaca at 

 S, S' ; Vr, renal veins. (After Wieder- 

 sheim.) 



