496 ALIMENTARY CANAL. 



(' Duodenum, 



Small intestine } Jejunum, 

 ( lleum. 



( Cascum, 



Large intestine < Colon, 

 ( Rectum. 



The Mouth is the irregular cavity which contains the organs of 

 taste and the principal instruments of mastication. It is bounded in 

 front by the lips ; on either side by the internal surface of the cheeks ; 

 above by the hard palate and teeth of the upper jaw ; below by the 

 tongue, by the mucous membrane stretched between the arch of the 

 lower jaw and the under surface of the tongue, and by the teeth of 

 the inferior maxilla; and behind by the soft palate and fauces. 



The Lips are two fleshy folds, formed externally by common in- 

 tegument, and internally by mucous membrane, and containing 

 between these two layers the muscles of the lips, a quantity of fat, 

 and numerous small labial glands. They are attached to the sur- 

 face of the upper and lower jaw, and each lip is connected to the 

 gum in the middle line by a fold of mucous membrane, the frsenum 

 labii superioris and fraenum labii inferioris, the former being the 

 larger. 



The Cheeks (buccas) are continuous on either hand with the lips, 

 and form the sides of the face ; they are composed of integument, 

 a large quantity of fat, muscles, mucous membrane, and buccal 

 glands. 



The mucous membrane lining the cheeks is reflected above and 

 below upon the sides of the jaws, and is attached posteriorly to the 

 anterior margin of the ramus of the lower jaw. At about its mid- 

 dle, opposite to the second molar tooth of the upper jaw, is a papilla, 

 upon which may be observed a small opening, the entrance of the 

 duct of the parotid gland. 



The Hard palate is a dense structure, composed of mucous mem- 

 brane, palatal glands, fibrous tissue, vessels and nerves, and firmly 

 connected to the palate processes of the superior maxillary and 

 palate bones. It is bounded in front and on each side by the alveolar 

 processes and gums, and is continuous behind with the soft palate. 

 It is marked along the middle line by an elevated raphe', and pre- 

 sents upon each side of the raphe* a number of transverse ridges 

 and grooves. Near the anterior extremity, and immediately behind 

 the middle incisor teeth, is a papilla which corresponds with the 

 termination of the naso-palatine canal, and has been supposed to be 

 endowed with a peculiar sensibility. 



The Gums are composed of a thick and dense mucous membrane, 

 which is closely adherent to the periosteum of the alveolar pro- 

 cesses, and embraces the necks of the teeth. They are remarkable 

 for their hardness and insensibility, and for their close contact, 

 without adhesion, to the surface of the tooth. From the neck of 





