162 ON LATERAL PRESSURE. 



the crown of the rising tooth, causes it to recede 

 as it emerges from the gum, and thus produces 

 just so much pressure as will be required to 

 separate the one from the other at their necks 

 when fully formed. The result of this is the sub- 

 sequent decay of one or both at the parts which 

 have thus come in contact. That teeth so crushed 

 together do, sooner or later, decay at the parts 

 injured, I believe to be an indisputable fact, 

 although we may not all agree as to the precise 

 manner in which this decay takes place, or upon 

 the agent by which it is immediately produced. 

 The peculiar distinctive features of the mischief 

 arising from this source may be readily traced in 

 the extent of the injury. When the distal surface 

 of the first or second molar is found to be decayed, 

 the cavity will generally extend down to the edge 

 of the gum, or even below it ; but not so with the 

 mesial surface opposed to it ; for this being the 

 offender and presenting a thickly enamel- coated 

 Fig. 16. surface, receives but a small 



amount of injury to itself, which 

 is principally confined to its most 

 prominent part, and often es- 

 capes almost unscathed. 



The above diagram, Fig. 16 (the original of which 

 is in the Society's museum), is a fair illustration of 

 these effects. Here, the second molar, having no 

 opportunity of moving forward out of the way of 



