INCISOR TEETH. 291 



A tooth consists of the following anatomical parts ; the body, or 

 crown, which is free of the gum, the grinding or cutting surface of 

 which is the table ; the cervix, or neck, the part invested by the 

 gum ; and the fang, or root, which is inserted into the socket or 

 alveolus. The alveoli are more porous, spongy, and vascular than 

 other bone ; they appear and grow with the teeth, and when these 

 decay, become absorbed They are lined by periosteum, which, 

 reflected from the gum, at the base of the socket, covers the fang, 

 communicating with the pulp cavity, which runs up the fang 

 centre, and contains a highly vascular and nervous organ, the pulp, 

 whence the dentine of the tooth grows. This pulp is enclosed in 

 -eular membrane, the dentine tubuli radiating from it. In 

 the aged tooth this membrane becomes ossified, forming the 

 secondary or osteo-dentine. The sensory nerve of the pulp 

 comes from the fifth pair; and it is owing to its extreme sensi- 

 bility that toothache is so severe when the pulp is exposed. 



Teeth are arranged alongside of each other, so as to form the 

 dental arches ; these are interrupted at each side, leaving the 

 interdental spaces, or diastemce. Teeth are of three kinds; the 



~ors, or cutting teeth, situated in front of the arches ; Cu 

 teeth, or tushes, in the interdental spaces : and Molars, or grinders, 

 behind. The horse, like many other animals, has two sets; the 

 temporary or milk teeth, and the permanent or horse teeth, the 

 former numbering 24, the latter 40. In the mare there are 

 usually 36 permanent teeth, the tushes being wanting or rudi- 

 mentary. 



INCISOR TEETH. 



The incisor or front teeth in the horse are 1 2 in number, 6 

 in each jaw ; the upper ones are the longer, their surfaces meet- 

 ing those of the lower ones ; in rare cases the former overlap, 

 constituting a " parrot mouth." The central pair are the largest, 

 the adjacent ones are called the middle, or lateral, while the 

 outer ones, which are the smallest, are termed the corner incisors. 

 The row of incisors forms a curve, which is part of the so- 

 called dental arch ; the younger the tooth the greater the 

 curvature, which gradually decreases with age. The anterior 

 surface of a young incisor tooth presents a triangular shape, with 

 the base at the table. Viewed laterally it is still triangular, but 

 its apex is at the table. The table is therefore oblong, its long 



