324 



THE TEETH. 



development to be enclosed in the base of the coronoid process of the lower jaTV, 

 and in the maxillary tuberosity in the upper jaw, but they afterwards succes- 

 sively assume their tdtunate position as the bone increases in length. The space 



Fig. 22i. 



Fig. 22'1. — The Teeth of a Child of Six Years, with the Calcified Parts of the 

 Permanent Teeth exposed (Allea Thomson, after Henle). 



The whole of the teeth of the right side are shown, together with the three front teeth 

 of the left side : in the upper and lower jaws the teeth are indicated as follows, viz. : — 

 1, milk-teeth—!, inner or first incisor ; i', outer or second incisor; c, canine ; m, first 

 molar ; m', second molar. 2, permanent teeth — I, inner or first incisor ; I', outer or 

 second incisor ; C, canine ; B, first bicuspid ; B', second bicuspid ; M', the first molar, 

 which has passed through the gums ; M-, the second molar, which has not yet risen above 

 the gums : the third molar is not yet formed. 



taken up by the ten anterior permanent teeth very nearly corresponds with that 

 which had been occupied by the ten mUk-teeth ; the difference in width between 

 the incisors of the two sets being compensated for by the smallness of the bicus- 

 pids in comparison -v^ith the milk-molars to which they succeed. Lastly, the 

 angle formed by the ramus and body of the lower jaw differs at different ages ; 

 thus it is obtuse in the infant, approaches nearer to a right angle in the adult, 

 and again becomes somewhat obtuse in old age. 



SECONDARY DENTINE. 



Under this head are included certain varieties of hard tissue liable to be formed 

 in the pulp-cavity of a tooth after the regular production of the dentine is com- 

 pleted. These, as hitherto noticed and described, are the following* : — 



1. Osteodentine (Owen). — This is a hard substance which becomes deposited 



* Salter, Guy's Hospital Reports ; and Dental Pathology and Surgery. 



