TE DIGKSTPVE SYSTEM. 
’ AMBROSE BIRMINGHAM. 
Unpur this head will be described the parts which are connected with the 
reception and mastication of the food, and its digestion and passage through the 
body. As the greater part of the digestive system is placed within the abdome on, 
the description of this cavity as a whole, with that of its lining membrane the 
peritoneum, will be included. 
The ELL parts of the digestive system may be grouped under the following 
heads, viz. 
L ‘The Alimentary Canal or Digestive Tube. 
2. The Digestive Glands. 
3. Accessory Parts. 
Alimentary Canal.—The alimentary canal, taken as a whole, measures about 
30 feet in length (Fig. 636), and consists of the following parts in order :—mouth, 
pharynx, cesophagus, stomach, small and large intestines. The mouth is the first 
division of the tube. It is separated from the nasal cavities above by the 
palate, and opens behind into the pharynx. This latter is an expanded portion 
of the canal lying behind both the mouth and the nasal cavity, the former 
opening into it ‘through the isthmus of the fauces, the latter through the posterior 
nares; whilst lower down, close to the base of the tongue, the aperture of the 
larynx is found on its anterior wall. Opposite the lower border of the larynx, 
the pharynx is succeeded by the esophagus, a long and comparatively straight 
portion of the digestive tube, ‘leading through the neck and thorax to the al \lomen, 
which it reaches by piercing the diaphragm. Immediately after entering the 
abdomen the tube expands into a pear-shaped dilatation, the stomach. This 
is followed by over 20 feet of small intestine, the junction of the two being 
marked by a constriction, the pylorus. The emall intestine presents three more 
or less arbitrary diy isions—namely, (a) the duodenum, a part about 10 inches in 
length, and curved somewhat like a horse-shoe, which is closely united to the posterior 
abdominal wall; (0) the jejunum, which includes the upper two-fifths, and (c) the 
ileum, the lower three-fifths of the small intestine beyond the duodenum. The 
jejunum and ileum are moyably suspended from the posterior abdominal wall by 
the mesentery, a fan-shaped fold of the peritoneum or lining membrane of the 
abdominal cavity. The terminal part of the ileum opens into the side of the large 
intestine, a few inches (2}) from the extremity of the latter. There is thus formed 
a cul-de-sac, the cecum, in connexion with which is found a small worm- shaped 
protrusion, the vermiform appendix. 
The orifice through which the ileum opens into the large intestine is guarded 
by the ileo-cecal valve, which prevents any return of its contents from the large into 
the small bowel. After the cecum comes the ascending colon, which runs up in 
the right side of the abdomen. This is succeeded in order by the transverse colon 
crossing from right to left, the descending colon running down on the left side, the 
sigmoid fiexure of the colon (which includes the iliac and greater part of the pelvic 
colons of the text), and finally the rectum, which opens on the surface at the anus. 
Digestive Glands.— Whilst the greater part of the alimentary canal 
is furnished with numerous minute glands contained entirely within its walls, 
C=) 
