ANATOMY IN A NUTSHELL. 311 



two jaws — twenty of the temporary set and twenty-eight of the permanent 

 set. The four wisdom teeth at this time are only embryonic buds. 



In a sagittal sectionof a tooth we see first the enamel (Plate CCXXVII) which 

 is the hardest structure in the body, consisting of 96.5 per cent earthy and 3.5 

 per cent animal matter. Its individual tubules are 55V0 of an inch in dia- 

 meter. Beneath the enamel is the dentine or ivory. The amount of earthy 

 matter is 72 per cent and the animal matter 28 per cent. Its tubules are 

 4^70 of an inch in diameter and are covered by the sheath of Neumann, which 

 protects it from the action of acids. The cavity in the tooth is called the pulp 

 cavity and contains the blood vessels but no lymphatics. The tissue in the 

 cavity is called myxomatous. The part which surrounds the root as the enamel 

 surrounds the crowm is called the crusta petrosa (Plate CCXXVII). 



There are two kinds of muscles found in the tongue (Plate CXLV) intrin- 

 sic and extrinsic. The intrinsic are the Superior lingualis, Inferior lingualis, 

 Transverse lingualis, and Vertical lingualis. They are all supplied by the 

 hypoglossal nerve. Some say the Inferior lingualis gets the Chorda-tympani 

 branch of the the seventh nerve. The extrinsic muscles are the Genio-hyo- 

 glossus, Palato-glossus, Hyo-glossus, Stylo-glossus, and Chondro-glossus. The 

 nerve to these is the hypoglossal. 



Papilla means a bud, a nipple, a teat, a pimple. The lingual mucous 

 membrane of the dorsum of the tongue is peculiar in several respects. It con- 

 sists of a layer of connective tissue forming a corium supporting special papilla? 

 covered with epithelium. The corium is a network in which ramify numerous 

 vessels and nerves. The papillae are of three kinds. 



LESSON LXXXVIII. 



1. Large circumvallate ("walled around") papillae seven in number set 

 in an inverted V at the back of the tongue and shaped like truncated cones set 

 on end in cup-like depressions, whence the name. (Plate CXLIII). 



2. Middie-sized fungiform ("mushroom shaped") papillae scattered irreg- 

 ularly over the surface, forming rounded red eminences like mushrooms, whence 

 their name. 



3. Small conical or filiform ("thread-shaped") papillae covering the an- 

 terior two-thirds of the surface, each ending in a number of little processes. It 

 is these that are concerned in the whitish coating or furring of the tongue. Be- 

 sides these papilla? there are several other simple ones. 



Occupying the entire thickness of the epithelium of the lateral surface of 

 the papilla? is a multitude of flack-shaped bodies, called tatse-buds. They are 

 composed of two kinds of epithelial cells, gustatory and sustentacular, packed 

 closely together. The microscopic structure of some papillae include certain 

 bodies called taste-buds. Taste-buds are scattered also over the dorsal surface 

 independently of papilla?, and are especially numerous in the posterior part. 



The nerves of the tongue are in four pairs. 1. The hypoglossal is 

 the motor nerve to the tongue. 



