68 THE HORSE IN HEALTH AND DISEASE 



due to poisoning from mercury, to a foreign body lodged in the 

 mouth, or to bad teeth. When horses are first turned into white 

 clover pasture increased salivation also often occurs. 



The hard palate is bounded in front and on each side by the 

 teeth, behind it is continuous with the soft palate (see Fig. 16). 

 On its surface is a median groove dividing it into two equal parts. 

 Twenty curved alternating grooves and ridges run across each 

 half; the concavity of these is backward. The ridges aid in retain- 

 ing the food when it is carried toward the back part of the mouth. 

 Swelling of the hard palate, sometimes noticeable in colts which 

 are teething, is commonly spoken of as "lampers," more correctly, 

 lam-pas. It is not a serious disease, and disappears when the irri- 

 tation subsides. 



The soft palate is a semimuscular organ suspended like a cur- 

 tain between the mouth and pharynx. It slopes downward and 

 backward from its junction with the hard palate. It presents two 

 surfaces and four borders, and is 5 or 6 inches long. The anterior 

 surface is toward the mouth, and the posterior toward the pharynx, 

 the anterior wall of which it forms. The lateral borders are at- 

 tached to the walls of the two cavities which the organ separates. 

 The superior border joins the hard palate, while the inferior is free 

 and in contact with the epiglottis, which may lie either in front 

 or behind the soft palate. Mucous membrane covers both sides 

 of the organ. During the act of swallowing it is raised to allow 

 the food to pass through. On account of its length in the horse 

 it is practically impossible for the animal to vomit through the 

 mouth. Instead, the material is passed along the posterior surface 

 of the soft palate and finds exit via the nasal cavity and nostrils. 

 This also explains why breathing does not take place through the 

 mouth. 



The isthmus of the fauces is the opening between the mouth 

 and the pharynx. Normally it is closed by the soft palate except 

 during deglutition. In man the tonsils are situated on the lateral 

 walls of this opening; in the horse the tonsillar tissue is distributed 

 over a larger area. 



The pharynx is a common organ of the digestive and respiratory 

 tracts. It is funnel shaped and is situated as a cross-roadj 

 between the nasal chambers and the larynx and the mouth and 

 the esophagus. Its walls are lined with mucous membrane, out- 

 side of which are voluntary muscles. There are seven openings 



