THE MOUTH, ORAL OR BUCCAL CAVITY 1217 



The enclosed mesoblastic papilla (the future dental pulp) has its peripheral cells, which are 

 called odontoblasts, differentiated into columnar bodies disposed as a layer, each cell having 

 a large nucleus. The vascular supply of the pulp is now well marked. A section of a follicle 

 at this period will exhibit the follicular wall springing from the base of the dental papilla and 

 having a well-marked blood supply. The bony alveolar walls are well outlined, and evidences of 

 a periosteum appear (Figs. 933, 934, and 935). 



Development of Enamel (Fig. 935). In point of time, the deposition of dentine actually 

 begins before that of enamel, so that the first-formed layer of enamel is deposited against a layer 

 of immature dentine, and is formed from within outward, so that the youngest enamel is upon 

 the surface of the tooth. The enamel is built up of two distinct substances globules of uniform 

 size which are formed by the ameloblasts, and a cementing substance, probably an albuminate 

 of calcium (calcoglobulin), the basis of all the calcified tissues. In the ends of the ameloblasts, 

 next to the dentine, the secretion of calcoglobulin is deposited, and into the plastic mass the 

 enamel globules are extruded, each globule remaining connected with the ameloblasts by plasmic 

 strings, which also join the globules laterally. 1 



ThV f f enamel 1 <rins in the tips of the cusps, and is quickly followed by a disap- 



pear +he stellate reticulum appears to atronHv. ' 3l 



tHp ^""'itVi 1~Hf* sl~T*ntnm '* 



becft.^Li,, niree and one-half inches (8.Y6 cm./ ft .^e the body, 



tissue, apex, dorsum, margin, and inferior surface. 



of The body (corpus linguae) forms the great bulk of the organ and is composed 

 *of striated muscle. 



The base or root (radix linguae) is directed backward and connected with the 

 hyoid bone by the Hyoglossi and Geniohyoglossi muscles and the hyoglossal mem- 

 brane; with the epiglottis by three folds, glossoepiglottic folds, of mucous membrane; 

 with the soft palate by means of the anterior pillars of the fauces; and with the 

 pharynx by the Superior constrictor muscles and the mucous membrane. 



The apex or tip (apex linguae) is free, thin, and narrow, and is directed forward 

 against the inner surface of the lower incisor teeth. 



The dorsum of the tongue (dorsum linguae) of a living person, when at 

 rest, is markedly arched from before backward. On the dorsum is a median 

 longitudinal raphe* (sulcus medianus linguae). This slight depression terminates 

 posteriorly in the depression known as the foramen cecum (foramen caecum linguae 

 [Morgagnii]), from which a shallow-shaped groove, the sulcus terminalis of His, 

 runs outward and forward on each side to the lateral margin of the tongue. The 

 part of the dorsum of the tongue in front of this groove, known as the anterior, 

 apical, or oral part, forming about two-thirds of its upper surface, looks upward, 

 is practically horizontal, and is rough and covered with papillae; the posterior or 

 basal third of the dorsum is vertical and looks backward, is smoother, and contains 

 numerous muciparous glands and lymphoid follicles. 



The margin of the tongue (margo lateralis linguae) is free in front of the anterior 

 arch of the palate. Just in front of the arch are several vertical folds, the folia 

 linguae. 



The under or inferior surface (fades inferior linguae) of the tongue is connected 

 with the mandible by the Geniohyoglossi muscles; from its sides the mucous mem- 

 jbrane is reflected to the inner surface of the gums, and from its under surface 

 p-m to the floor of the mouth, where, in the middle line, it is elevated into a distinct 

 toertical fold, the frenum linguae (frenulum linguae). To each side of the frenum 

 'I 1 a slight fold of the mucous membrane, the plica fimbriata, the free edge of which 

 , 10 :hibits a series of fringe-like processes. 

 IO iThe tip of the tongue, part of the under surface, its sides, and dorsum are free. 



men 



like tincture of the Tongue. The tongue is partly ves ^i^ggg^. i: a S3 } ?^ I ^^ a i^ 



have ntf fibrous layer surrounding the central muscle g-^. b&ck of the ^^ ^ These 

 are three \ from each other, in the middle hijp^ and are termed fhe sup eradded permanent 

 teeth. Tires arranged i& various $~ the permanent set, the molars of the temporary set being 

 replaced by the premolars or bicuspids of the permanent set. 



1 J. L. Williams, Dental Cosmos, 1896. 

 77 



