256 THE VISCERA. 
which lies near the medial border and the opening of which is 
the hilus. It contains the pelvis (@) (the expanded beginning 
of the duct of the kidney), and also renal vessels (¢ and /) with 
their branches. These structures are enclosed in fat, which fills 
the remainder of the sinus. Upon opening the pelvis the 
kidney substance is seen to project into it in the form of a cone, 
the papilla (c), the apex of which is directed mediad. On the 
apex of the papilla are the numerous openings of the uriniferous 
collecting-tubes, some of them opening at the bottom of an 
apical depression of the papilla. 
In a section made parallel to the ventral surface and in the 
median plane, the substance of the kidney is seen to consist of 
a peripheral darker and more granular cortical portion (Fig. 
109, 4), and of a central, lighter, less granular medullary 
portion (2). Both portions are marked -by lines which con- 
verge to the apex of the papilla (c). 
THE URETER (Fig. 108, c; Figs. 111 and 112, 6).—The 
duct of the kidney begins as the pelvis (Fig. 109, @), a coni- 
cal sac the base of which encloses the base of the papilla. 
From the apex of the papilla the urine passes into the pelvis. 
The outer wall of the pelvis is continuous with the capsule of 
the kidney. At the hilus the pelvis narrows to form the ureter 
(Fig. 109, g). The ureter passes caudad in a fold of peri- 
toneum which contains fat. Near its caudal end it passes 
dorsad of the vas deferens (Fig. 111, ¢), turns ventrocraniad, 
and pierces the dorsal wall of the bladder (Fig. 111, a) 
obliquely near the neck. On the inside of the bladder the 
openings of the ureters appear as pores about five millimeters 
apart, and each is surrounded by a white, ring-like elevation 
of the surface. 
THE BLADDER. VESICA URINARIA.—The bladder (Fig. 
III, @) is pear-shaped. It lies in the abdominal cavity between 
its ventral wall and the rectum and a short distance craniad of 
the pubic symphysis. Caudad it is continued into a rather 
long, narrow neck (/) which passes dorsad of the symphysis 
to the pelvic cavity. 
The bladder is covered by peritoneum and is held in place 
by its neck and by three folds of the peritoneum. One of these 
