THE ALIMENTARY CANAL. 221 
sheets which bound this area constitute the coronary ligament 
of the liver. This ligament is broader where it passes from the 
left lateral lobe to the diaphragm and is called the triangular 
ligament. (There is perhaps a corresponding right trangular 
ligament, from the cranial division of the right lateral lobe.) 
The caudal division of the right lateral lobe is held to the 
kidney of that side by the hepatorenal ligament. 
II, THE ALIMENTARY CANAL, APPARATUS DIGESTORIUS. 
The alimentary canal may be divided into mouth, pharynx, 
cesophagus, stomach, small intestine, and large intestine. 
With thesé are associated certain accessory structures,—the 
salivary glands, the liver, and the pancreas. The spleen, 
though not belonging to the digestive system, is usually 
described in connection with it. The respiratory organs are 
almost throughout in close relation with the organs of the 
digestive system. 
1. The Mouth. Cavum oris.—The mouth cavity extends 
from the lips to the pharynx. It is narrower toward the lips, 
broadens caudad as far back as’ the last teeth, then becomes 
narrowed to form the isthmus faucium, by which it communi- 
cates with the’ pharynx. The mouth cavity is divisible into 
the vestibule of the mouth (vestibulum oris), which comprises 
that part outside the jaws proper, bounded externally by the 
lips and cheeks, and the mouth cavity proper (cavum oris 
proprium), which lies within the teeth. That portion of the 
vestibule which is bounded by the cheeks is sometimes farther 
distinguished as the buccal cavity. The entire mouth cavity 
(except the teeth) is lined by the mucous membrane or mucosa. 
The lips (labia oris) are thick folds of skin bounding the 
entrance to the mouth cavity. The outer surface is covered 
with hair; the inner surface is covered with the mucous mem- 
brane. The upper lip is marked in the median line by a deep 
external groove which extends upward to the septum of the 
nose. Along the inner surface of this groove the lip is closely 
united to the jaw by a thick fold, the frenulum of the upper 
lip. For some distance on each side of the frenulum the inner 
