ARISTOTLE'S MISTAKE. 69 



Monsieur Lecoq's description of the grinder teeth, 

 like the one just quoted, is a contribution to dental 

 science. The repetition of facts already given is off- 

 set by its additional facts, and its historical informa- 

 tion is as interesting as are Prof. Owen's comparisons. 

 It is as follows (" Traite de FExterieur du Cheval et des 

 Principaux Animaux Domestiques") : 



" It was believed for a long time that the grinders of 

 Solipeds were all persistent teeth. This error, founded 

 on the authority of Aristotle, was so deeply rooted that, 

 although Ruini, toward the end of the Sixteenth cen- 

 tury, had discovered the existence of two temporary 

 molars, Bourgelat did not believe it when he founded 

 the French veterinary schools, and was only convinced 

 when Tenon proved by specimens, in 1770, that the 

 first three are deciduous. (A mistake. See p. 294.) 



" Generally considered, the grinder arcades have not 

 the same disposition in both jaws. Wider apart in the 

 superior one, they form a slight curve, whose convexity 

 is outward. In the inferior jaw, on the contrary, the 

 two arcades separate in the form of a V toward the back 

 of the mouth. Instead of Coming in contact by level 

 surfaces, the grinders meet by inclined-planes. In the 

 lower jaw the internal border is higher than the exter- 

 nal, while the reverse is the rule in the upper. This 

 circumstance prevents the lateral movement of the 

 lower jaw taking place without separation of the inci- 

 sors, and thus saves them from friction. 



" Like the incisors, each grinder presents for study 

 a free and a fixed portion. The free portion (the body), 

 nearly square in the upper grinders, broader than 

 thick in the lower, shows at the external surface of the 

 former two longitudinal grooves, the anterior of which 



