_P._, Pylorus; _G.b._, gall-bladder; _R.K._, right kidney; _L.K._,
left kidney; _P._, (above duodenum) pancreas; _Bl._, urinary
bladder; _V.s._, vesicula seminalis; _B.g._, bulbo-urethral
(Cowper’s) gland. Costal attachment and median line of diaphragm are
indicated by dotted lines.
]
[Illustration:
FIG. 295.—LIVER OF OX, PARIETAL SURFACE; HARDENED _in situ_.
]
The =colon= is about 35 feet (ca. 10 m.) long; its diameter is at first
about the same as that of the cæcum, but diminishes to about two inches
(ca. 5 cm.). Its capacity is about 6 to 8 gallons (ca. 25 to 30 liters).
With the exception of its first and terminal parts, it is arranged in
double elliptical coils between the layers of the mesentery; the
adjacent parts are therefore alternately centripetal and centrifugal
(Gyri centripetales et centrifugales). The first part (Ansa proximalis)
is marked off from the cæcum only by the ileo-cæcal opening; it forms an
=S=-shaped curve and is continued by the spiral part (Ansa spiralis).
The coils of this are attached to each other by connective tissue, and
are best seen from the inner side. The bowel gradually diminishes in
caliber, and the terminal part (Ansa distalis) leaves the spiral mass,
passes forward to the great mesenteric artery and turns backward between
the duodenum and the initial sigmoid part. From the ventral surface of
the right kidney it passes backward, forms an =S=-shaped curve near the
pelvic inlet, and joins the rectum; this part is attached to the
sublumbar muscles by a short mesentery, and is also attached to the
dorsal part of the duodenum.
The =rectum= is somewhat shorter than that of the horse, and is usually
covered with peritoneum as far back as the first coccygeal vertebra. The
retroperitoneal part is surrounded by a quantity of fat. The anus is not
prominent.
[Illustration:
FIG. 296.—LIVER OF OX, LEFT MARGINAL VIEW; HARDENED _in situ_.
]
The =serous coat= is of course absent on the adherent surfaces of the
spiral part of the colon. There is a large amount of fat in the
mesentery. The =longitudinal muscular coat= is evenly distributed,
consequently there is no sacculation of the bowel. There is a valvular
mucous fold at the ileo-cæcal orifice. A Peyer’s patch occurs in the
beginning of the cæcum and one in the first part of the colon.