THE CHARACTERS FURNISHED BY THE TEETH. 655 



The surface of friction of the intermediates is completely formed. 

 (Plate XVII.) 



Five Years. The mouth is made, full; the incisive arch is a 

 regular semicircle. All the permanent teeth have reached the same 

 level in both jaws. The anterior border of the corners touches and 

 begins to wear ; the posterior is not worn. (Plate XVIII.) 



Five Years Past. The preceding characters on the pincers-and the 

 intermediates are more marked. It is especially from the full develop- 

 ment and the freshness of the corners that this age is determined. The 

 posterior border of these teeth in the superior incisive arcade is only 

 commencing to wear. The jaws form a regular semicircle, convex in 

 front and from above to below, when examined in profile from the side. 



Fourth Period. Levelling of the Permanent Incisors. 

 The signs furnished during this period by the dental apparatus already 

 become more difficult to recognize. The determination of the age also 

 now becomes more uncertain than in the preceding period. The prin- 

 cipal points to be examined are the degree of wear of the corners, the 

 form and transverse diameter of the incisor teeth, and the form and 

 situation of the central enamel in relation to the posterior border of 

 the tables of friction. Finally, too much stress should not be laid 

 upon the indications, often fallacious, of the levelling of the teeth, the 

 disappearance of the so-called " mark," which is nothing more than 

 the external portion of the external dental cavity colored black, and 

 filled sometimes with alimentary matter. 



Six Years. Very marked levelling of the pincers, whose table 

 tends to assume the oval form. Wearing of the posterior border of 

 the corners, and the formation of a complete circle of central enamel 

 around the external dental cavity. The latter, in the intermediates, is 

 almost worn away to its bottom, and sometimes even these teeth are 

 completely levelled. The cement is now commencing to disappear 

 from the anterior face of the pincers, especially towards the anterior 

 border, which makes them appear whiter than at five years. (Plate 

 XIX.) [The corner incisor is very often a shell tooth, its posterior 

 border being entirely absent. In such a case, a six-year-old can be 

 recognized by the fact that not only the anterior border but also its 

 external extremity are decidedly worn.] 



Seven Years. The layer of cement which covers the anterior 

 face of the incisors is worn off, so as to show the pearly tint of the 

 enamel. The inferior corner, narrower from in front to behind than 

 the superior, wears off the table of the latter, so as to form on it a 

 noteh towards its posterior part, more or less visible according to the 



