IRREGULARITIES OF THE DENTAL APPARATUS. 749 



external border that it can bruise the aliment against the internal border 

 of the superior arcade, when the jaws are tightly closed. These two 

 regions of the left arcades will therefore be the only ones exposed to 

 wear, while the opposite parts of these same arcades, not exposed to 

 friction, will continue to increase in length. Suppose, now, any perma- 

 nent cause whatsoever (periostitis, caries, fistula, lesions of the cheek, 

 the tongue, etc.) prevents, by the pain which accompanies it, mastica- 

 tion on the left side, and we will have the conditions for the production 

 of the irregularity in question. The tables, being no longer worn out- 

 wardly for the superior molars and inwardly for the inferior, will 

 acquire an excessive length at these points, and will become more and 

 more obliquely bevelled outward and downward. The effect, becoming 

 a cause in its turn, will be superadded to the action of the primitive 

 lesion ; the tables on the right side will remain normal, while those 

 on the left will cross each other like the blades of a pair of shears. 



The gravity of these bevelled molars depends upon the nature of the 

 difficulties which the dental irregularity opposes to mastication, and 

 which may even extend to lesions of the hard palate. 



They may pass unperceived at the time of purchasing the horse, 

 if the buyer neglects to examine the mouth. The state of the in- 

 cisors will, nevertheless, arouse suspicions, the plane of meeting of 

 these arcades not being regular ; in fact, these teeth always appear 

 short on one side and long on the other. This characteristic, of itself, 

 is sufficient to direct attention to the molar arcades. 



c. Irregularities on the Surface of the Molar Dental 

 Tables. For some obscure reasons, probably the absence of the nor- 

 mal movements of propulsion and retropulsion of the jaws, the molar 

 arcades, no longer gliding against each other in the longitudinal di- 

 rection, become covered with prominences more or less extensive and 

 elevated, which are lodged in corresponding cavities on the opposite 

 molar tables. 



These irregularities of the surfaces of friction are generally attribu- 

 table to a ravenous appetite, swallowing the food without mastication, 

 and the slight consistence of the food. Under the influences of all 

 these causes mastication is very rapid, the jaws make a simple up-and- 

 down movement, and the tables are not worn smooth by the action of 

 the two sets of teeth gliding against each other. 



The softer constituents of the teeth are worn away and become hol- 

 low, while the harder parts preserve their length and even continue to 

 increase. The effect, eventually becoming a cause, contributes more and 

 more to augment the primitive inequalities, so that at a certain period 



