THE TEETH OF MAN. 



shut over and in front of the lower teeth, concealing the 

 upper thirds of their crowns ; while the- 



of the bicuspids and molars_j3f_the lower jaw are received 

 into the depressions between theexternal amir-internal 

 4fee similar teeth in the upper jaw, thus allow- 



ing the--^xtHrliaIjLiibeefeft*^f i the upper teeth to close ex- 

 ternally to the outer ttlfreTcles^ef the lower row. 



From this arrangement of the tubercles, we are enabled 

 in mastication to use the whole surface of the crowns of the 

 opposing teeth ; the act of mastication being performed by 

 bringing tb^ external tubereles of- the under molars opposite 

 to those of the upper row ; W&&B, by the lateral motion 

 of the under jaw inwards, ffirif QTitaraal tubnrnlrrT^rr^^TTTrn 

 the inclined surfaces of the external,- and up those of tho 

 'ntnrnnl tnhnrfiltirirfthn njrpnr tiathj ftrrmftfigrim t 1 - 1 '-" n n ^ 

 any interposed substance. 



It will also be observed that, from the difference of width 

 in the incisors of the two jaws, the central incisors of the 

 upper extend over the centrals and half of the laterals of 

 the under row, and that the superior laterals lie over the 

 remaining half of the inferior laterals and the anterior half 

 of the canines of the lower jaw. The canines close over the 

 halves of the canines and first bicuspids, while the first bi- 

 cuspids impinge on the half of the first and half of the second 

 bicuspids of the lower row. The second upper bicuspids 

 close upon the anterior third of the opposing first molars 

 and the posterior half of the second bicuspids. 



The first molars oppose the posterior two thirds of the 

 first, and one third of the second molars of the lower jaw, 

 while the second upper molars close upon the unoccupied 

 posterior third of the second and the anterior third of the 

 wisdom teeth. The wisdom tooth of the upper being 

 smaller in size than that of the lower jaw is perfectly 

 opposed by that portion of the latter left unoccupied by 

 the second upper molar tooth. 



