The cavity is subdivided into three re gions, thc epigastric, which includes all the space above an imaginary line drawn acrossthe b elly, from the greatest convexi tie§ of the cartilages of the seventh true rib; the umbilical, which is the divisiOn between this line and another drawn from the anterior super,ior spines of the ilia ; and the hypogastric, which is the space left below the last line.
The sides of the epig-astric region, which are the spaces covered by the car tilages of the ribs, are called hypochon dria: the sides of the umbilical region are named the loins : and those of the hypo gastric the groins.
The stomach is a large membraneous reservoir, rec eiving the food from the ceso phagus, and retaining it until a certain change, called digestion* produced. Its figure is cortical, as it is largest at the left end, and gradually decreases in size to wards the right: these are called the great er and smaller extremities of' the stomach. It is also bent inits course, so that we describe a greater and smaller curvature or arch. It has two Openings, one close to the diaphragm, called the cardiac, su perior, or cesophageal ; the other, just at the smaller end, is called the pyloric, or lower orifice. The capacity of the sto mach varies from about 5 to it pints.
Its structure is muscular; and this is ' necessary in order to propel the food when digested. Under the muscular coat is found the internal, or villous, tunic; the arteries of which pour out the gastric juice, the chief agent in the digestion of the food:.
The pylorus, which word is derived from two Greek terms, signifying the keeper of the gate, is a contracted ring, by which the stomach communicates with the small intestine. It prevents the food from passing out of the stomach before it has been sufficiently acted on by the gastric juice, The stomach receives a portion of peri toneum as the cesophagus passes the dia phragm. There is also a process coming from the liver, called the lesser omenttufi, or mesogaster. This is attached to the lesser arch of the stomach. The great ornentum, or the caul, is affixed to thr greater arch of the stomach, and hangs from thence over the suiface of the intes tines, being interposed between them and the parietes. It IS also attached to a part of the colon : its use is unknown.
The smallintestine is divided into three parts; the duodenum, jejunum, and ileum: but this distinction is an arbitrary one, and not founded on any difference in struc ture. It consists of a membranous tube,
about an inch, or an inch and a half in di ameter, and four times the length of the subject. Notwithstanding this great length, it is collected, by means of numerous turn ings and convolutions, into a comparative. ly small space. These convolutions of the small intestine occupy the chief part of the umbilical and hypogastric regions of the abdomen. They are connected in their situation by means of a broad folded membrane, called the mesentery. This production of the peritoneum is about six inches broad at its commencement, but it expands gradually, something after the manner of a fan, so that it becomes broad enough, ultimately, to cover the whole length of the small intestine. It serves to keep the different convolutions of the ca nal in a certain relative position, and al lows, at the same time, a considerable freedom of motion, without any danger of intangling. In tracing the course of the small intestine, we follow the duodenum from the lesser extremity of the stomach, in the right hypochondrium, making three turns close on the backbone, and then coming out just over the left kidney. The general direction of the canal from this point, independently of its various turn ings and windings, is towards the right groin, where the ilium terminates by en tering' the ececum.
The small intestine possesses three coats similar to those of the stomach, viz. an ex-ternal or peritoneal ; a middle or muscular ; and an internal, or villous, tu nic. The latter forms a great many trans verse, loose, and floating processes, call ed valvulz conniventes ; by means of which the extent of surface of the villous eoat is very much augmentett Numerous glandular bodies are found in parts of the canal, collected hitto small parcels, and kence called glandulz digminatz.
The food which is redneed by the ac tion of the stornarilo into an homogeneous mass, called chyme, cnters the small ?In testine, where it undergoes a further change, and becomes chyle. It is pro pelled along the canal .by the muscular *oat of the intestine, and the vinous tu nic absorbs from it the mUltiolls Parti cles. It passes along every tiThi and wind ing of this long calla], continually subject ed to the action of the absorbing vessels. The residue of the alimentary matter is sent into the lafge intestine, trom which it is expelled in the form of fxces.