IRREGULARITIES OF THE DENTAL APPARATUS. 739 



As we have already stated, the variations of length are of two 

 orders : the excess and the insufficiency. V\q will first study the former. 



a. Excess of Length of the Crown. 



This anomaly presents the following variations : 



a. Incisors too Long in both Jaws. — In specimens deposited 

 by us in the museum of the Alfort School, we have found an excess of 

 length of nineteen to twenty-two millimetres for the superior teeth 

 and fifteen to eighteen millimetres for the inferior. 



The direction of such teeth, as a rule, closely approaches the hori- 

 zontal, for, were it otherwise, the superior molar arcade could no longer 

 be brought in contact with the inferior. Their free extremities are a 

 little divergent, and, on this account, the arcades are somewhat fan- 

 shaped. The surface of friction still resembles that of early years ; 

 flattened from before to behind, it tends to assume an oval form ; as 

 to the central enamel, it occupies a large area upon the dental table, 

 and a small external dental cavity on the inferior corners often still 

 exists. 



The excessive length of the crown, in such conditions, is not in 

 relation with that of the root.; the teeth, less firmly implanted, are 

 much more liable to break. Besides, they do not mark the real age, 

 and might deceive the observer who only makes his inferences from the 

 dental tables, without having recourse to the procedure indicated by 

 Pessina and Girard. * 



To determine the correct age of the horse it suffices to shorten, 

 in imagination, the teeth which are too long. This means, easy of 

 employment if the successive forms of the dental table at the different 

 periods be recalled, enables one to arrive at an estimate, if not exact, 

 at least very approximative. 



Sawing or rasping off the incisors which, in old horses, have ac- 

 quired an excessive length, a procedure often practised by horse- 

 dealers, with a view of making them appear younger than they really 

 are, does not deceive the expert. An attentive purchaser should 

 not thus be deceived, since, by this means, he is spared the mental 

 operation of shortening the teeth, which we have just recommended. 

 But the layman may be influenced by this trick, for he is imbued with 

 the idea, very correct otherwise, that the exaggerated length of the 

 teeth coincides, to a certain extent, with the animal's age. 



b. Incisors too Long in the Superior Jaw alone. — Tliis 

 anomaly constitutes what is vulgarly called parrot mouth, or croio 

 mouth, bee de perroquet (Fig. 319), by reason of the resemblance of the 



