OF THE CLASS MAMMALIA. 263 



fine black colour, is common throughout the fertile countries 

 of Europe. 



418. The order rodentia comprises the ordinary ongui- 

 culated mammals which have no canine teeth, but have strong 

 chisel-shaped teeth in front, or incisives, andmolar teeth behind. 



Fig. 204. The Common Campagnol. 



This arrangement of the teeth (Fig. 205) adapts them for 



gnawing very hard vegetable substances, as the bark and 



roots of trees, and these in fact 



form their principal nourishment. 



The brain of rodents resembles 



greatly that of the insectivora, 



and their intelligence is very 



confined; nevertheless, some are 



gifted with extraordinary instincts. 



Squirrels (Fig. 100), marmots, 



rats, hamsters (Fig. 101), the 



campagnol (Fig. 204), the porcu- T 



r /T?- i^-i\ i i ji Fig. 20o. Head of a Rodent . 



pine (Fig. 172), and several other 



animals, similarly organized, belong to the order rodentia. 



Rodents of the genus rat are characterized by some pecu - 

 liarities in the disposition of the teeth, and by their long 

 and scaly tail. They are small animals, and live especially 

 on fruits and roots, but, pressed by hunger, they take to 

 animal food, and will even attack and devour each other. 

 Three species have become common in our houses ; the domestic 

 rat, the surmulot, and the mouse. 



The rat was not known to the ancients, and seems to have 

 been imported into the Old World from America. The epoch 

 of its introduction is unknown, but it existed in great num- 

 bers where the surmulot now abounds. This latter seems to 

 have almost extirpated the common rat. It is now very rare 



