28 THE SURGICAL ANATOMY OF THE HORSE 



remaining ones ; moreover, these teeth are easily distinguished from 

 those of the upper jaw, inasmuch as they present only one longitudinal 

 groove on their outer aspect, and that is faintly marked. 



The number of fangs varies. Each of the end molars in both jaws 

 possesses three fangs, whilst the remaining molars in the superior 

 maxilla possess four, and those in the inferior maxillary bones only 

 two fangs. These fangs are only formed when the remainder of the 

 tooth is completely developed, and the filling up of the alveolus has 

 commenced, the crown being in wear. 



In the unworn tooth, the table presents a very undulated appearance, 

 but the outer layer of enamel covers everywhere the underlying dentine, 

 and lines the two fosss or infundibula, which extend to a considerable 

 depth into the tooth. As the tooth becomes worn therefore an external 

 ring of enamel is present, enclosing the internal rings. Owing to the 

 irregularity in outline of the tooth these rings are likewise very irregular. 

 The enamel, being the densest of the three substances of which the tooth 

 is composed, wears much more slowly than the dentine and cement, with 

 the result that the rings of enamel stand out prominently above the 

 cement and dentine as thin, hard, irregular ridges. The arrangement of 

 the rings is thus easily noted, and it has been very aptly compared with 

 the Gothic " B " with a small appendage. 



In the teeth of the lower jaw no dentine is visible between the inner 

 portion of the outer ring of enamel, and the corresponding portions of 

 the rings of the infundibula, since these layers towards the inner side 

 of the tooth are continuous with one another. 



The roots of some of the molars project into the maxillary sinuses, 

 where they are covered by a thin layer of bone. This is an important 

 surgical point, which will be referred to later in describing the removal 

 of diseased molars. 



Four teeth are frequently present which are placed one in front of 

 each first molar. These are the so-called ijcolf's teeth. Each is 

 developed in the same dental groove as the corresponding row of molars. 



