300 



ATTACHMENT. 



of the Capybara and Elephant have the crown cleft into a numerous 

 series of compressed transverse plates, cemented together side by 

 side. 



The ordinary teeth of the Mammalia have so much more 

 definite and complex a form, than those of Fishes and Reptiles, 

 that three parts are usually recognized in them, viz., the fang, 

 the neck, and the crown. The fang or root (radix) is the inserted 

 part, the crown (corona), the exposed part, and the constriction 

 which divides these is called the neck, or cervix. The term, * fang,' 

 is properly given only to the implanted part of a tooth of restricted 

 growth, which gradually tapers to its extremity ; those teeth which 

 grow uninterruptedly have not their exposed part separated by a 

 neck from their implanted part, and this generally maintains to its 

 extremity the same shape and size as the exposed crown. 



It is peculiar to the class Mammalia to have teeth implanted 

 in sockets by two or more fangs ; but this can only happen to teeth of 

 limited growth, and generally characterizes the molars and premolars. 



127. Attachment. — In no mammiferous animal does anchylosis 

 of the tooth with the jaw constitute a normal mode of attachment. 

 Each tooth has its particular socket, to which it firmly adheres by 

 the close co-adaptation of their opposed surfaces, and by the firm 

 adhesion of the alveolar periosteum to the organized cement, which 

 invests the fang or fangs of the tooth : but in some of the Cetacea^ at 

 the posterior part of the dental series, the sockets are wide and 

 shallow, and the teeth adhere more strongly to the gum than to the 

 periosteum : in the Cachalot I have seen all the teeth brought away 

 with the ligamentous gum, when it has been stript from the sockets 

 of the lower jaw. 



True teeth implanted in sockets are confined, in the present 

 class, to the maxillary, intermaxillary, and lower maxillary bones, 

 and to a single row in each. They may project only from the 

 intermaxillary bones as in the Narwhal ; be apparent only in the 

 lower maxillary bone, as in the Cachalot ; or be limited to the superior 

 and inferior maxillaries, and not present in the intermaxillaries, as 

 in the true Pecora, and most Bruta of Linnaeus ; in general, teeth are 

 situated in all the bones above mentioned. In Man, where the inter- 

 maxillaries early coalesce with the maxillary bones, where the jaws 



