334 THE DIGESTIVE APPARATUS IN MAMMALIA. 



tissue, shows numerous conical papillae, especially at the posterior part of 

 the palate. The epithelium fills up the depressions between the papilhe ; it 

 is stratified and squamous, and remarkable for the great thickness of its 

 horny layer. 



3. Two voluminous arteries the palatine or palato-labials lodged in the 

 bony fissures of the palatine roof. These arteries proceed parallel to one 

 another, and unite in front by anastomosing to form a single trunk, which 

 enters the incisive foramen. It is of importance to know their disposition in 

 a surgical point of view, as care ought to be taken not to wound them when 

 abstracting blood from the palate. The blood carried by these arteries 

 arrives in the deep-seated erectile membrane, and is finally removed by two 

 very short venous trunks, which do not pass with the palato-labial arteries into 

 the palatine canal, but only into the palatine fissure. 



4. Sensory nerves which accompany the arteries, and are derived from the 

 superior maxillary branch of the fifth pair of cranial nerves. 



FUNCTIONS. The palate has a passive, but important, share in mastica- 

 tion and deglutition ; furnishing the tongue, as it does, with a firm basis in 

 the movements it executes when passing the food between the molar teeth, 

 and in carrying the alimentary mass backwards to the pharynx. 



4. The Tongue. (Figs. 149, 152.) 



Preparation. 1. By means of a strong saw without a back, make an antero-posterior 

 and vertical section of the head, in order to study the general disposition of the tongue. 

 2. From another head remove the lower jaw, leaving the tongue in the intermaxillary 

 space, to examine the external conformation of the organ (see the dissection of the 

 palate). On a third head, kept for the study of the muscles, these parts are exposed in the 

 following manner : The masseter is entirely removed, and the cheek is detached from the 

 lower jaw and folded back on the upper jaw ; then the branch of the inferior maxilla is sawn 

 through transversely, at first behind, next in front of the molar teeth : the upper piece ot 

 bone should be detached by luxating it behind the temporo-maxillary articulation, after des- 

 troying the capsular ligament and dividing the insertions of the pterygoid muscles. With 

 regard to the inferior piece, it is reversed in such a way as to put the line of the molars 

 downwards, and the inferior border of the -bone upwards in the bottom of the inter- 

 maxillary space. To do this it is sufficient to separate the buccal mucous membrane from 

 the mylo-hyoideus muscle, proceeding from above to below. The dissection thus 

 prepared, serves not only for the study of the muscles of the tongue, but also for those of 

 the deep salivary glands, the pharynx, larynx, guttural pouches, the nerves and arteries 

 of the head, etc. It is always better, in order to facilitate this dissection, to keep the 

 jaws apart by fixing a piece of wood or bone between the incisor teeth immediately after 

 the death of the animal. 



The lingual canal. The inferior wall of the mouth (or floor), circum- 

 scribed by the lower alveolar arches, forms an elongated cavity named the 

 lingual canal (or space), which lodges the organ designated the tongue. This 

 canal occupies, in its anterior third, the superior face of the body of the lower 

 maxilla. For the remainder of its extent, it is formed by a double groove, 

 which is directed to the bottom of the mouth, at the sides of the tongue. It 

 exhibits the sublingual crest and the barbs, of which we will speak when 

 describing the sublingual and maxillary glands. 



Situation of the tongue. The tongue occupies the whole length of this 

 elongated cavity, and thus extends from the back part of the mouth to the 

 incisor teeth, lying in the intermaxillary space, where it rests on a species of 

 wide sling formed by the union of the two mylo-hyoidean muscles. 



External conformation. It is a fleshy organ, movable in the interior of 

 the buccal cavity, and almost entirely enveloped by the mucous membrane 

 which lines that cavity. In Solipeds, it forms a kind of triangular pyramid. 



