THE TEETH 



1119 



hexaeonal prisms [prismata adamantina] which are arranged perpendicular to the surface and 

 are of epithehal origin. In adult teeth, the enamel is often worn through m places, exposing 

 the yellowish dentine. The dentine of the root is covered by a thm layer of cementum [sub- 

 stantia ossea], a layer of bone which is very thin at the neck, but becomes thicker toward the 

 root apex (fig. 873). Surrounding the root is the alveolar periosteum a fibrous membrane 

 connecting the cementum firmly with the bony lining of the socket. For further details of 

 the minute structure of teeth, works on histology may be consulted. 



Gums.— Covering the alveolar portions of the maxilla and mandible are the 

 gums [gingiva]. They are continuous with the mucosa of the vestibule exter- 



FiG 873 —Vertical Section of an Inferior Canine Tooth, in Situ. X 4. (From 



Toldt's Atlas.) 



Gum 



Transition from mandibular to 

 alveolar periosteum 



Dental pulp 

 Pulp capillaries 



Vein 

 Artery 



Nerve twigs 



Alveolar periosteum 

 Cementum 

 Dental alveolus 



Compact bone of mandible 



Vascular and nerve bundle 

 for the pulp 



Marrow spaces of mandible 



nally and of the palate or floor of the mouth internally. Like the mucosa of the 

 mouth elsewhere, they are covered with stratified squamous epithelium. The 

 lamina propria is especially thick and strong, and is firmly attached to the sub- 

 jacent bone. Around the neck of each tooth, the epithelium of the gum forms an 

 overlapping collar and the lamina propria is continuous with the alveolar perios- 

 teum (fig. 873). _ . . . ., 

 The incisors.— (Figs. 868, 869, 870, 874.) The incisor teeth [dentes mcism] 

 are so named on account of their function in cutting the food. The crown has a 



