NATURAL HISTORY OF SOUTH AFRICA 



grow continuously throughout life. This provision 

 of Nature is essential to the life of a Rodent animal, 

 for, owing to constant use in gnawing hard sub- 

 stances, such as wood, these teeth, which are for 

 the most part composed of soft ivory, would soon 

 wear down to the gums. If, however, an accident 

 should happen to one of the lower front teeth, the 

 corresponding upper one, meeting with no resist- 

 ance, will continue to grow, and eventually be the 

 cause of the animal dying a lingering death. Many 

 such instances are on record. A live Ground 

 Squirrel was sent to me in the last stages of starva- 

 tion. On examination it was seen that one of the 

 lower incisor teeth was missing, and the correspond- 

 ing upper one had grown so long that the animal 

 was unable to eat. In the Port Elizabeth Museum 

 we have the skull of a Blesmol showing an upper 

 incisor tooth which, owing to an injury to the 

 corresponding lower incisor, had grown in a semi- 

 circle, and the point had imbedded itself firmly in 

 the base of the animal's palate. It is more common 

 for an upper or lower incisor to get broken, and 

 before it can grow the proper length to come in 

 contact with its counterpart in the opposite jaw, 

 the other has grown unduly long and curved 

 inwards, so that when the broken tooth grows, it 

 fails to come in contact with the point of its fellow, 

 and continues growing, with the result that the 

 upper and lower incisor teeth grow abnormally 

 long. We have such an example in the Port 



