This section is from the book "Animal Physiology: The Structure And Functions Of The Human Body", by John Cleland. Also available from Amazon: Animal Physiology, the Structure and Functions of the Human Body.
The Stomach is succeeded by the small intestine, a tube about twenty feet long, and having a breadth of about an inch and a half at the commencement, and an inch at its termination. For about the first ten inches it is bound down in a crescentic form to the back of the abdomen; and this part is termed the duodenum, and has the bile duct, and the duct of a large gland, called the pancreas, opening into it close together about its middle. The remainder of the small intestine is not connected with the abdominal wall, except through the medium of the mesentery—a fold of the peritoneum or lining membrane of the abdomen, containing within it vessels and nerves. The upper third of this part of the intestine gets the name of jejunum (empty), from usually containing little but the pulp sent down from the stomach, and here termed chyme. But the more fluid portions of the chyme get absorbed as it descends, and in the lower two-thirds of the small intestine, the ileum, the contents are consequently usually more solid. The ileum opens into the large intestine in the region of the right groin.