THE INCISORS. 619 



termediates, and the latter from the corners, are well marked, and 

 enable us to ascertain with the greatest ease the changes which have 

 taken place. To observe this, it suffices to separate the lips of the 

 animal and to examine the mouth from in front. 



The following facts result from the preceding phenomenon, concern- 

 ing the general direction of the teeth : 



1st. That the incidence of the arcades increases in obliquity with 

 the age. 



2d. That their curvature and their transverse diameter diminish. 



3d. Finally, that the roots, at first converging, become parallel, 

 then diverging, while the free extremities approach each other and 

 leave between themselves, at their base, a triangular space occupied by 

 the gum, so much the more exaggerated as the animal increases in age. 



The Tusks or Canine Teeth. 



Four in number in the adult horse, and situated between the in- 

 cisors and the molars, the tusks are absent or but little developed in 

 the mare, as a rule. Formerly, those which were provided with canines, 

 called brehaignes, were wrongly considered as being sterile. 



Does each one of the two dentitions present canines ? 



It is rather difficult to answer this question with precise accuracy. 

 Girard mentions that Rigot and Forthomme have observed deciduous 

 canines. The latter showed him jaws which, independently of these 

 deciduous teeth, presented behind the latter their two replacing teeth 

 stripped of their alveolus. Rigot said that this fact was not rare, and 

 that he had seen it not infrequently in colts three or four years old. 

 As to Girard, he had never witnessed it. 



If the teetli of colts be examined, there is constantly found in the two 

 sexes, in the place of the canines, very small teeth which are exceedingly 

 thin and needle-like. Are these the deciduous canines ? This is prob- 

 able ; but it is certain that if these teeth simulate them in position, they 

 do not at all possess their particular form. The facts of Rigot and 

 Forthomme should therefore be regarded as very exceptional. In the 

 absence of a detailed description, it is not out of place to ask if these 

 were not abnormal instances of double canines. We are rather in- 

 clined to adopt this latter opinion, having witnessed a case of this kind 

 in an old ass, of which we will represent the inferior jaw (Fig. 290). 



A short time after their eruption the canines have the general form 

 of a cone, and are curved upon themselves in the direction of their 

 length. There is no well-defined limit between the crown and the 



