ON LATERAL PRESSURE. 175 



although we have hitherto contrasted only the 

 extremity of both forms, others will be found 

 merging from one into the other in every stage of 

 gradation, with more or less difference in their 

 relative proportions. 



In the third and remaining source of lateral 

 pressure, its occurrence may be attributed to 

 accidental circumstances producing imperfect an- 

 tagonism of the teeth. 



In a perfect " bite," we have everywhere a series 

 of inclined planes in opposition. This is espe- 

 cially apparent in the bicuspides, the point of 

 one cusp fitting in between the oblique sides of 

 the two opposed to it. The "stop" which pre- 

 vents the mouth closing beyond a certain point, is 

 effected by the molars, and when these have 

 become so arranged, by the loss of some of them, 

 that there are none remaining in antagonism, the 

 bicuspides have a tendency to separate, and exert 

 a destructive amount of lateral pressure against 

 their neighbours, if such there happen to be. Or 

 it will sometimes be seen that the bicuspides, as 

 well as the cuspids and incisors, have become pro- 

 jected forwards, and the former will then press 

 upon each other, so as to decay at the parts in 

 contact, while the latter — the cuspids and in- 

 cisors, especially in the upper jaw — ultimately 

 become excessively prominent, and either loosen 

 from the absorption of the socket, and fall out of 

 themselves, or require removal. 



