

DENTITION. 485 



The first molar tooth, on each side, from the twelfth to the 

 fourteenth month ; 



The cuspated, from the fifteenth to the twentieth month; 



The second molar, on each side, from the twentieth to the 

 thirtieth month.* 



The Deciduous teeth, by a process which will be presently ex - 

 plained, drop from the gums and are succeeded by the perma- 

 nent teeth. The first permanent molar, about six or seven years 

 of age, by emerging behind the second infant molar, leads the 

 way to the second epoch of dentition which occurs in the fol- 

 lowing order: 



The central infant incisors fall out about the sixth or seventh 

 year, and are immediately followed by the central perma- 

 nent incisors ; 



In a few months afterwards, sometimes at the same period, 

 the lateral infant incisors tumble out, and are succeeded by the 

 lateral permanent incisors; 



About the ninth year the first molar teeth fall out, and are 

 succeeded by the first bicuspated ; 



From the ninth to the eleventh year, the second molars fall 

 out, to be succeeded by the second bicuspated; 



From the eleventh to the twelfth, the infant cuspated are fol- 

 lowed by the adult cuspated ; 



About the end of the twelfth year, the second permanent 

 molars protrude behind the first permanent; 



And, finally, from the sixteenth to the twenty-fifth year, the 

 third permanent molars or the Dentes Sapientias, make their 

 appearance. . 



In the jaw of a fcetus of three or four months after conception, 

 the beginning of the alveolar processes may be observed, in the 

 condition of a longitudinal groove, deeper and more narrow in, 

 front, more shallow and wider behind; and in the bottom of the. 

 groove are small transverse ridges, dividing it into superficial 

 depressions. From this simple condition, ridges begin to shoot 

 out from the opposite sides of the canal near its brim ; and form, 

 by their junction, arches across it; more matter being added to 

 these arches, they make, in their progress, a sort of cell for each 



* Serres, loc. cit. 



41* 



