THE UROGENITAL S YSTEM. 255 
IV. THE UROGENITAL SYSTEM. APPARATUS UROGENI- 
TALIS. 
1. The Excretory Organs. 
KipNnEY. REN (Figs. 108 and 109). 
The kidneys of the cat are compact (i.e., not lobulated) and 
have the usual kidney or bean form. They lie in the abdomi- 
nal cavity, one on either side of the vertebral column, against 
the dorsal body wall, in the region between the third and fifth 
lumbar vertebrze. The right kidney is one or two centimeters 
farther craniad than the left, and the long axes of the two con- 
verge craniad a little. Each is covered by peritoneum on 
its ventral surface only (i.e., it is retroperitoneal). At the 
border of the kidney, where the peritoneum passes from it to 
the body wall, there is an accumulation of fat, which is most 
abundant at the cranial end of the kidney. Within the peri- 
toneal investment the kidney is enclosed in a special loose 
fibrous. covering, the capsule or tunica fibrosa, which is con- 
tinuous with the fibrous coat of the ureter and pelvis. In the 
middle of the median border of each kidney is a notch, the 
hilus. It gives exit to the ureter (Fig. 108, c) and renal veins 
Fic. 108.—Lrerr KIDNEY, VENTRAL Fic. 109.—MEDIAN LONGITUDI- 
SURFACE. NAL SECTION OF KIDNEY. 
Fig. 108.—a, renal artery; 4, renal vein; ¢, ureter. 
Fig. 109.—-a, medullary portion; 4, cortical portion; ¢, papilla; ¢, pelvis; ¢, renal 
artery; 7, renal vein; g, ureter. 
(2), and entrance to the renal artery (a). On the ventral sur- 
face of the kidney within the capsule are seen grooves radiating 
from the hilus. They contain blood-vessels. If the substance 
of the kidney is sliced away parallel to the ventral surface for 
some distance (Fig. 109), there is exposed a cavity, the sinus, 
