THE COELOM, DIGESTIVE, AND RESPIRATORY SYSTEMS 185 



The hard palate is supported by the premaxillary, maxillary, and palatine bones, 

 as should be recalled from the study of the skull. The soft palate lacks 

 bony support. The mucous membrane of the hard palate is thrown into a 

 number of roughened transverse ridges. At the anterior end of the hard palate 

 just behind the incisor teeth will be found a pair of openings, the openings of the 

 nasopalatine ducts which connect the mouth and nasal cavities by way of the 

 incisive foramina of the maxillary bones. The opening of the duct of the parotid 

 gland may be sought for on the inside of the cheek opposite the second upper 

 premolar tooth in the rabbit, opposite the last cusp of the third upper premolar 

 of the cat, in which animal it is situated on a slight ridge: the openings are 

 difficult to identify with certainty and not much time should be spent in looking 

 for them. 



The floor of the oral cavity is occupied by the tongue, a fleshy muscular 

 organ, more mobile in mammals than in most other vertebrates. The anterior 

 margin of the attachment of the tongue to the floor of the mouth has the form of 

 a vertical fold, the frenulum. Halfway between the lower incisors and the frenu- 

 lum will be found in the rabbit the two small slitlike openings of the ducts of the 

 submaxillary glands, the two being about an eighth of an inch apart. In the cat 

 a fold runs forward from the frenulum on each side just within the teeth, and 

 terminates anteriorly in a well-marked flattened papilla which bears the openings 

 of the ducts of the submaxillary and sublingual glands. 



Cut through the floor of the mouth on each side, keeping the scalpel next 

 to the mandible. The tongue can now be pulled down and out between the two 

 halves of the lower jaw. The cuts may be continued on each side at the base of 

 the tongue back to the level of the submaxillary glands so that the tongue can 

 be pulled well down. The surface of the tongue may now be examined in detail. 

 In the rabbit the tongue is divisible into two portions, an anterior softer portion, 

 covered with minute pointed elevations, the fungiform papillae; and a posterior, 

 elevated, smoother, and harder portion. At the posterior end of the latter on 

 each side is situated a vallate papilla, consisting of a round elevation set into a 

 pit. In front of each vallate papilla on the side of the tongue is an oval area of 

 considerable size marked by numerous fine parallel ridges, the foliate papilla. 

 In the cat the anterior part of the tongue is covered with the filiform papillae, 

 many of which are hard and spinelike, pointed posteriorly; the remainder of the 

 tongue is provided with fungiform papillae; among the fungiform papillae are 

 four to six vallate papillae arranged in two V-shaped rows, each consisting of a 

 round elevation set into a pit. At the sides of the vallate papillae are some very 

 large fungiform papillae. The papillae are provided with microscopic taste buds. 

 c) The pharynx: The pharynx is that portion of the cavity lying posterior 

 and dorsal to the soft palate. Pull the tongue well forward and examine the 

 soft palate. It descends like a curtain across the posterior end of the oral cavity. 

 Find its free posterior margin, arching above the base of the tongue. (The 



