The intestine is short—about five or six times the length of the body.
The =small intestine= has an average length of about thirteen feet (ca.
4 meters). It occupies most of the abdominal cavity behind the liver and
stomach. The duodenum begins at the portal fissure and passes backward
and upward, at first on the visceral surface of the liver, then in
contact with the right flank. Near the pelvis it turns inward and
sharply forward, passes along the inner border of the left kidney, and
joins the jejunum to the left of the root of the mesentery. The
mesoduodenum is given off from the common mesentery; it is a relatively
wide fold, except at the terminal part. Here there are two short folds,
one of which joins the mesocolon; the other passes on to the terminal
part of the colon. The first part of the mesoduodenum contains the right
branch of the pancreas. Its root is blended with the mesocolon to form a
common mesentery. The remainder of the small intestine forms numerous
coils, and is attached by a wide mesentery to the sublumbar region. The
=pancreatic= and =bile-ducts= open into the duodenum about two or three
inches (ca. 5 to 8 cm.) from the pylorus; the =accessory pancreatic
duct= opens an inch or two (ca. 2.5 to 5 cm.) further back. The mucous
membrane has very long villi. The duodenal (Brunner’s) glands occur only
near the pylorus. Peyer’s patches are numerous (about twenty in young
subjects), and begin in the duodenum. They are usually elliptical in
outline, but the last one is band-like, reaches to the end of the ileum
and is four to sixteen inches (ca. 10 to 40 cm.) long in young dogs
(Ellenberger). There is an ileo-cæcal valve.[117] The muscular coat is
relatively thick.
[Illustration: