Page:Laboratory Manual of the Anatomy of the Rat (Hunt 1924).djvu/84

70 ward from the hard palate. The surface of the soft palate bears small papillae. The palate is widest at the posterior part of the molar tooth region, decreasing in width forward to the inturned lobes of the upper lips, and backward to the pharynx. A membranous ridge, the palatine arch (pillar of the fauces), extends ventrally from the posterior end of the soft palate on each side of the isthmus faucium. The hard palate bears eight transverse ridges, the most anterior of which is ventral to the prepalatine foramina. The three anterior ridges are the largest and lie in front of the molar teeth. The other five ridges are within and behind the molar region. These five may assume approximately the form of a letter w, with the base of the letter forward, or the form of a bow, or of an obtuse angle whose anteriorly directed apex lies in the mid-dorsal region of the palate. Each of the five ridges bears a row of short spines throughout its length. Other denticulated ridges, which do not reach the median line of the hard palate, may also be present. At the posterior end of the hard palate is a triangular area bearing spines.

Carefully disarticulate the lower jaw. The tongue is an elongated muscular organ extending from the pharynx forward to the incisor teeth. It fits snugly into the floor of the mouth between the molar teeth. Anterior to the molars it is unattached to the mouth floor. The vertical frenulum which in some animals connects this anterior free region of the tongue with the mouth floor is absent. A median dorsal furrow extends seven or eight millimeters back from the tip. The tongue is attached to the floor of the mouth from the anterior molar teeth caudad. The proximal one-sixth of the organ is attached on both sides also, so that it alone forms the floor at the back of the mouth. The tongue unites with the hyoid bone a short distance in front of the epiglottis.