3PLANCHNOLOGY 



their ducts opening for the most part into the fossae of the vallate papillae. These glands are 

 racemose, the duct of each branching into several minute ducts, which end in alveoli, lined by 

 a single layer of more or less columnar epithelium. Their secretion is of a watery nature, and 

 probably assists in the distribution of the substance to be tasted over the taste area. (Ebner.) 



The septum consists of a vertical layer of fibrous tissue, extending throughout the entire 

 length of the median plane of the tongue, though not quite reaching the dorsum. It is thicker 

 behind than in front, and occasionally contains a small fibrocartilage, about 6 mm. in length. 

 It is well displayed by making a vertical section across the organ. 



The hyoglossal membrane is a strong fibrous lamina, which connects the under surface of 

 the root of the tongue to the body of the hyoid bone. This membrane receives, in front, some 

 of the fibers of the Genioglossi. 



Taste-buds, the end-organs of the gustatory sense, are scattered over the mucous membrane 

 of the mouth and tongue at irregular intervals. They occur especially in the sides of the vallate 

 papillae. In the rabbit there is a localized area at the side of the base of the tongue, the papilla 

 foliata, in which they are especially abundant (Fig. 1021). They are described under the organs 

 of the senses (page 991). 





Central lamina of 



corium 

 Lateral lamina in which 



nerve fibers run 

 Gustatory calyculus 



Sinus-like vein travers- 

 ing whole length of 

 folium 



Nerve bundles 



Serous gland 



*****.* Nerve bundles 



FIG. 1021. Vertical section of papilla foliata of the rabbit, passing across the folia. (Ranvier.) 



Vessels and Nerves. The main artery of the tongue is the lingual branch of the external 

 carotid, but the external maxillary and ascending pharyngeal also give branches to it. The 

 veins open into the internal jugular. 



The lymphatics of the tongue have been described on page 696. 



The sensory nerves of the tongue are: (1) the lingual branch of the mandibular, which is 

 distributed to the papillae at the forepart and sides of the tongue, and forms the nerve of ordinary 

 sensibility for its anterior two-thirds; (2) the chorda tympani branch of the facial, which runs 

 in the sheath of the lingual, and is generally regarded as the nerve of taste for the anterior two- 

 thirds; this nerve is a continuation of the sensory root of the facial (nervus intermedius) ; (3) the 

 lingual branch of the glossopharyngeal, which is distributed to the mucous membrane at the 

 base and sides of the tongue, and to the papillae vallatse, and which supplies both gustatory 

 filaments and fibers of general sensation to this region; (4) the superior laryngeal, which sends 

 some fine branches to the root near the epiglottis. 



The Salivary Glands (Fig. 1024). Three large pairs of salivary glands communi- 

 cate with the mouth, and pour their secretion into its cavity; they are the parotid, 

 submaxillary, and sublingual. 



Parotid Gland (glandula parotis). The parotid gland (Figs. 1022, 1023), the largest 

 of the three, varies in weight from 14 to 28 gm. It lies upon the side of the face, 

 immediately below and in front of the external ear. The main portion of the gland 

 is superficial, somewhat flattened and quadrilateral in form, and is placed between 

 the ramus of the mandible in front and the mastoid process and Sternocleidor 

 mastoideus behind, overlapping, however, both boundaries. Above, it is broad 

 and reaches nearly to .the zygomatic arch; below, it tapers somewhat to about 



