THE TEETH 27 



and the infundibulum is present at first, but it is very shallow and 

 consequently soon disappears as the tooth is worn. 



Permanent teeth, on tlie other hand, are much larger, and on the 

 anterior surface of the crown there is present a well-marked vertical 

 groove. The tooth tapers gradually from the crown to the fang, so that 

 there is no well-defined constriction or neck. The infundibulum is wide 

 and deep, and surrounded by a fairly thick layer of enamel. 



The Molars 



In the permanent dentition there are twelve cf these in each jaw, six 

 on either side. The two rows in the superior maxillary bones are more 

 widely separated from one another than are those in the inferior maxilla. 

 Moreover, the tabular surfaces of the former are directed obliquely 

 downwards and outwards, whilst those of the latter take an oblique 

 direction, which is upwards and inwards. The inner edge of the lower 

 molars is therefore higher than the outer, and the outer edge of the 

 upper molars extends to a much lower level than the inner edge. 



Each molar presents a free exposed portion and a portion concealed 

 in the alveolus. 



The molars of the upper jaw are all fixed in alveoli, which are 

 situate in the superior maxillary bones. The free portion of each of 

 these molars presents four surfaces and an inclined base which represents 

 the table. The surfaces are almost equal to one another in breadth, so 

 that a transverse section of the tooth would be approximately square 

 in outline. 



The outer surface shows two parallel and longitudinal grooves, which 

 are continued on to the concealed portion of the tooth, and of which the 

 anterior is much the deeper. The inner surface presents only one such 

 groove, which is very shallow, but which also runs longitudinally. 



A transverse section of one of the lower molars would be oblong in 

 outline, as the outer and inner surfaces are much broader than the 



