[From the Foreign Scientific Journals], 



Professor Meisner, of Basle, has recently given some account of the pro- 

 digious growth of incisor teeth, in some of the Rodentia, which he thus accounts 

 for. These teeth, in their normal state, are continually growing in length, slowly 

 rising in height from the alveola, in such proportions as become requisite to com- 

 pensate for the daily wearing away of their chisel-formed edges. This growth 

 not ceasing during life, he remarks that all such teeth are invariably tubular at 

 their base ; and that the same effect is produced not only in the incisor teeth, but 

 in all others whose roots remain unclosed. In animals — such as the Elephant, 

 Babiroussa, Hippopotamus, and Narwal, — where these bony productions serve as 

 a defence, the same observation seems fully to apply ; and they sometimes attain 

 an enormous length, no given measure having been ascribed to them for the full 

 period of their maturity, that depending solely upon the duration of the animal' s 

 life. In the molar teeth of Hares, Rabbits, the Beaver, and some other Rodents, 

 this fact holds equally good ; but it is not so in the domestic Rat, Mouse^and 

 others, in which the alveola is always closed ; he cites the observations of Blimen- 

 bach on the monstrous growth of the molar teeth of a Hare, examined b^him, 

 and also those of Rudolphi on a similar lusus in an Indian Pig. We have fully 

 confirmed these observations by an examination of several extraordinary examples 

 of this phenomenon in the matchless Museum of the College of Surgeons. In a 

 Rabbit, we observed the incisor teeth to have grown in a spiral form : in a Hare, 

 also, in which, from their position, they must have occasioned the animal's death, 

 by entering the head, or pressing so firmly upon it, at either side, as to wound 

 the flesh and penetrate it. It thus appears clear that a beautiful provision of 

 Nature is exhibited in the formation of these teeth ; their continual increase ena- 

 bles them to preserve a fine, even, cutting edge, always set to a particular angle 

 with each other, so long as they remain truly in opposition ; the motion of gnaw- 

 ing or cutting their food, having also the effect of keeping the teeth sharp, by 

 means of their constantly slipping over each other. If, however, by any accident 

 or malformation of parts, these teeth cease to act against each other, their growth 

 still going on, they form a curved line, extending to an indefinite length during 

 the animal's life, and occasioning no doubt, in many instances, premature disease 

 and death. So perfect is Nature in all her mechanism, that the slightest deviation 

 from it, by accident or other causes, produces fatal effects. 



