medulla 

 cortex _I collecting ducts 



papilla projecting 

 nto pelvis 



medulla (collecting ducts not shown) 



M lateral ridges 

 of crest 



A UNILOBULAR WITH PAPILLA B UNILOBULAR WITH CREST C UNILOBULAR-PAPILLA WITH D CREST IN 



LATERAL RIDGES CROSS SECTION 



POLYLOBULAR COMPACT 



F CENTRAL CREST WITH TERMINAL RECESSES 

 (WEAKLY POLYLOBULAR) 



minor calyx 



major calyx 



H POLYLOBULAR WITH REDUCED PELVIS AND EXPANDED 

 TERMINAL RECESSES 

 Figure 10-1. Variations in the internal structure and form of the mammalian kidney. (Mainly after Gerhardt, 1914) 



POLYLOBULAR LOOSE 



one kidney and a crest in the other. Among primates, the 

 chimpanzee has a papilla; the orang and gorilla have a 

 crest, while man has a number of papillae opening into 

 calyces of the pelvis. 



Next in order of increasing complexity, the outer surface 

 of the kidney reveals the individual lobules as in the covvf, or 

 the lobules may be even more distinct as in the seal. In the 

 whale, Physeter, the lobules are quite separate within the 

 capsule. Each lobule is a renculus ("little kidney") with the 

 calyces appearing as tubules leading to the ureter (Figure 

 1 0-1 G). Another modification is observed in the kidney of 



the horse, which is indistinctly polylobular and compact 

 with a crest extending into the pelvis. The pelvis, however, 

 has tubular extensions, each called a recessus terminalis, 

 reaching into the anterior and posterior parts of the elon- 

 gated kidney. These extensions receive the collecting tubules 

 of the indistinct lobules of the ends of this kidney. A similar 

 type is seen in the Dugong (Sirenians), but here the lobuli 

 are distinct and separated by columns of Berlin. The central 

 pelvis is much reduced and inconspicuous, and the recessi are 

 large spaces. 



The ureter extends from the pelvis of the kidney to the 



292 . THE UROGENITAL SYSTEAA 



