in certain of the Mammalia rodentia. 



ultimate cause of the evil may arise from other accidents 

 besides those above mentioned. Thus, it may originate from 

 too soft food ; from a morbid and too rapid secretion of the 

 osseous matter of the tooth, which is constantly being deposited 

 at its root, or from some slight derangement of the under jaw ; 

 such as, for instance, a dislocation of one of its condyles, where- 

 by the incisors of that jaw would be thrown out of their proper 

 position, and their cutting edges could not be brought fairly 

 into contact with those of the opposite pair. In either of 

 these cases, the growth of the teeth will be over-proportioned 

 to their abrasion by the acts of gnawing and feeding, and a 

 preternatural elongation of that part which is above the gums 

 will immediately take place. It is obvious that this diseased 

 growth will be more or less rapid according to the degree of 

 influence exerted by the predisposing cause, and the length of 

 time it has operated. Perhaps, in the first stage of the malady, 

 its progress may be very gradual, and not much interfere with 

 the usual habits of the animal; but the teeth having once 

 attained such a length that, under any circumstances, their 

 edges cannot be brought to act upon each other, their growth 

 must be much more rapid, and ultimately prove such an 

 inconvenience, as must often terminate in the starvation of 

 the sufferer. 



It is to one of the above causes that I would attribute this 

 singular accident in the two following instances, in neither of 

 which was there any deficiency in the proper number of teeth, 

 or appearance of their having 

 been broken. 



In the first of these rab- 

 bits, which is preserved in the 

 museum of the Cambridge 

 Philosophical Society, and is 

 a remarkably fine example of 

 the anomaly in question, the 

 lower incisors are the pair 

 chiefly elongated (7%. 31.); 

 and they are here so prodi- 

 giously developed, as to turn 

 completely over the nose, 

 measuring in length, from the 

 surface of the gum to their 

 cutting edges, no less than two 

 inches and one eighth. * I 

 am inclined to suggest, that, 

 in this case, it was a too rapid secretion of the osseous matter 



* The usual length of this portion of the incisor in the wild rabbit is 

 only three lines, or a quarter of an inch. 



