MAMMALIA 275 



gland, a gland which lies below and in front of the eye. On 

 the inner side of the angle of the jaw is the submaxillary gland, 

 the duct of which, Wharton's duct, runs along the mandible 

 to open into the mouth just in front of the tongue. The 

 sublingual gland lies at the side of he tongue near its anterior 

 end and discharges by several ducts into the mouth in that 

 region. 



The saliva is an alkaline fluid containing salines and mucin, 

 and it possesses also the ferment ptyalin which acts upon 

 starch, converting it into maltose. Thus a beginning is made 

 in digestion in the mouth, but the main function is to soak 

 the food and thus help in its mastication and, after that is 

 accomplished, in swallowing it. 



The mouth cavity is bounded externally by the lips and 

 the dental arch, between which that is to say, between the 

 inner wall of the cheek and the gum lies the narrow space 

 called the vestibule. It is roofed above by the palate, which 

 is resolved in front into the bony palate and posteriorly into 

 the soft palate. The latter ends in the median uvula and the 

 archway leading to the pharynx, and in this archway on 

 each side lies the pit containing the tonsil. The floor of 

 the mouth is occupied by the large muscular tongue, and it is 

 attached to the floor over the greater part of its length, being 

 free only in front. On its upper surface are papillae concerned 

 in the sense of taste. 



The pharynx lies behind the mouth and "presents also the 

 openings of the posterior nares. Posteriorly it opens below 

 into the windpipe or trachea and above into the oesophagus. 

 The opening into the trachea is guarded by a stiff elastic 

 tongue-like structure which projects upwards behind the 

 tongue. This is the epiglottis. In the act of swallowing, the 

 epiglottis is believed to bend backwards and thus form a bridge 

 over the opening into the trachea, but in several mammals 

 it is evident that the food passes on each side of the projection. 

 When the food is swallowed it is conveyed quickly by peri- 

 staltic action to the stomach. The oesophagus passes down 

 the neck dorsal to the trachea, and, traversing the medial 

 plane of the thorax, it pierces the diaphragm, and the tube 

 immediately expands into the stomach. It is lined, like the 



