In the New World pouched rats (Geomyidae) the pouches open externally on the cheeks.
The pine-marten appears to have been partially domesticated by the Greeks and Romans, and used to keep houses clear from rats and mice.
As for the reasoning powers in animals, the accounts of monkeys learning by experience to break eggs carefully, and pick off bits of shell, so as not to lose the contents, or of the way in which rats or martens after a while can no longer be caught by the same kind of trap, with innumerable similar facts, show in the plainest way that the reason of animals goes so far as to form by new experience a new hypothesis of cause and effect which will henceforth guide their actions.
Voles, as typified by the water-rat and the tailed fieldmouse, are stouter built and shorter-nosed rodentsthan the typical rats and mice, with smaller ears and eyes and shorter tails; all being good burrowers.
Rats should be exterminated as far as possible, especially by means of the Danysz virus, which spreads a disease amongst rats which cannot be communicated to man.
This genus contains a few clumsily built rats spread over Southern Asia from Palestine to Formosa, and from Kashmir to Ceylon (see Bandicoot-Rat).
They have very small eyes, blunt snouts, inconspicuous ears and short limbs and tails, in all of which points they are markedly contrasted with true rats and mice.
The typical rats and mice, together with their nearest relatives, constitute the sub-family Murinae, which is represented by more than three hundred species, distributed over the whole of the Old World except Madagascar.
In porcupines and hares the tendons of the flexor digitorum longus and flexor hallucis longus are connected in the foot, while in the rats and squirrels they are separate, and the flexor digitorum longus is generally inserted into the metatarsal of the first toe.
On account of certain structural peculiarities, the rats of Madagascar, which have a dentition like that of the cricetine Muridae, are separated as a distinct family, Nesomyidae.