Others, lastly, have a tolerably regular set of teeth, presenting quadriacuminate molars, mostly small canines, and rodent-like incisors—Shrews and Bats.
Order 1. Gedärm-, Eyer, Schleimthier-Haarthiere—Rodentia.
3565. Rodent teeth, without canines.
The dental formula of the gnawing Rats and Mice is so varied, and so devoid of influence upon their bodily structure and mode of life, that all attempts to arrange these animals in accordance with it have failed.
3566. The lower position of the Rodentia admits of being easily proved by taking to our aid the meaning of the dental system. The splanchnic or visceral teeth obviously rank lower than the membral teeth. Now, it so happens that the anterior teeth are in the Rodentia the principal organ, not only of the dental formula, but of the entire animal. Without gnawing-teeth the Mice could not maintain their existence, much less their character. They thus depend wholly and solely upon the visceral teeth, and are consequently the lowest Thricozoa.
In addition to this comes their small size, which is by no means a character to be despised, and one to which all naturalists pay regard, even while they keep it, upon the other hand, in the background; or else they must place the Elephant below the Field-mice.
3567. I divide them, as well according to structure as habit, into three groups. The one has the front and hind feet of equal length, with blunt claws for digging.
The other has similar feet, with sharp claws for climbing.
Lastly, the third has the hind feet longer than the fore for leaping.
Fam. 1. Infusorial Thricozoa—Wühlmäuse.