IRREGULARITIES OF THE DENTAL APPARATUS. 747 



superior jaw when an excess of wear has made them too short. In- 

 stances of this kind are more rare. We present one in Fig. 323. 

 The separation of the roots here is also less common, and the bands 

 of enamel persist longer. It would be superfluous to go into fuller 

 details. 



p. Excess of Length of the Crown. 



The irregularities from excessive length of the molars are as com- 

 mon as the preceding. As they may exist in both jaws, and as they 

 give rise to the same considerations, we will examine them in a general 

 manner. 



a. Sharp Spiculse of the External and Internal Borders 

 of the Molar Arcades. The excess of length, but slightly marked 

 in the simpler cases, alters only the external or the internal borders of 

 the surfaces of friction. It is then manifested by asperities in the 

 form of sharp spiculce or points appearing upon the external border 

 of the tables of the superior molars, and the internal border, on the 

 contrary, of those of the inferior molars. These roughnesses, by their 

 prominence, lacerate the internal face of the cheeks and cut the lateral 

 surface of the tongue ; they cause, for this reason, severe pain, which 

 interferes with the regular mastication and necessitates dressing of the 

 teeth. 



The presence of these irregularities may prove to be an obstacle to 

 the normal lateral movements (diduction) which the jaws describe. 

 This impediment is nearly always due, as has been pointed out by 

 H. Bouley, 1 to the gluttony of the subjects or to their ravenous appe- 

 tite. Mastication in them is hasty, and is accomplished simply by an 

 up-and-down or chopping movement of the jaws. This is all the more 

 decided as the aliment on which the animal feeds is less difficult of 

 trituration. The superior molar tables, which are wider, and normally 

 overlap the inferior, no longer rub against the latter at their whole 

 extent, and become covered with sharp points at the level of the part 

 not worn, their external border. The impediment of which we speak 

 can be remedied, in most instances, by the tooth-rasp or a few cuts of 

 the tooth-plane. 



b. Bevelling of the Molars. Molaires en Oiseaux. The 

 molar teeth are subject to irregularities much more grave, and already 

 pointed out by Girard, 2 by H. Bouley, 3 and by us. 4 



1 H. Bouley, Nouveau Dictionnaire de mSdecine, de chirurgie et d'hygiene v6te>inaires, t. 

 iv. p. 622, Paris. 1858. 



2 Girard, Traite de 1'Age du cheval, p. 49. 3 H. Bouley, loc. cit. 



4 G. Barrier. Sur les molaires en riseaux, in Bulletin de la Soci6t6 centrale de medecine 

 veterinaire, p. 82; Kecueil de medecine veterinaire, anne 1887. 



