IRREGULARITIES OF THE DENTAL APPARATUS. 741 



superior jaw to the corresponding mandible of the parrot or the 

 crow. 



The teeth, in this case, not only have acquired an excessive length, 

 which may reach ten centimetres, but they are greatly curved forward 

 and downward, while their posterior face is cut by a sharp bevel from 

 the friction of the inferior incisors. 



The latter are generally shorter than in a normal state, and the 

 " parrot beak" is formed almost regularly by the pincers and the inter- 

 mediates on both sides of the arcade, the corners participating much 

 less in this respect than their neighbors. Nevertheless, it may happen, 

 as is seen in the jaw represented in the figure, that the irregularity 

 is more marked on one side than on the other. In this case, the in- 

 ferior teeth, which do not correspond to the projection formed by the 

 superior, are longer than in ordinary conditions. 



In certain horses five years of age, the superior jaw overlaps, for a 

 few millimetres, the inferior, while behind the surfaces of friction cor- 

 respond at their whole extent. The wear, therefore, spares the anterior 

 border of all the superior incisors, especially the pincers and the inter- 

 mediates. We think that there results from this, in time, first a more 

 decided prominence of this border, then a more or less elongated bevel, 

 and, finally, a true parrot mouth. Those who have had the oppor- 

 tunity of observing such horses during a number of years could easily 

 throw some light upon this interesting point. 



However this may be as to its varieties of form and its genesis, the 

 parrot mouth is observed only in very old horses. It interferes more 

 or less, according to its degree, with the prehension of food, especially 

 that of the grains, for its prominence considerably hinders the action 

 of the lips. The jaws become comparable, in a manner, to a pair of 

 pincers or tongs whose branches overlap each other. Besides, their 

 maximum separation has no longer the same proportion. While the 

 buccal opening, in a normal state, is ten to eleven centimetres, we have 

 found only two centimetres between the pincers of tlie two arcades, in 

 the jaws represented above. 



In such a state the determination of the age is almost impossible. 

 We must depend mainly upon the characters relative to the direction, 

 the color, and the width of the teeth, or, finally, shorten the latter, 

 in imagination, to their ordinary length. When the bee de perroquet 

 is too long and too inconvenient, it may be necessary to resort to 

 mechanical means to shorten the superior arcade. This operation, 

 which is done by means of a saw, is not very difficult when practised 

 upon the living subject. Besides the immediate advantage which it 



