OP PLANTS AND ANIMALS. 155 



between the two countries, as there is nothing in their 

 organization to convey them in such abundance to such vast 

 distances from their native localities. 



Some species of animals have also a very extensive 

 geographical range. The muskrat is found from the mouth 

 of Mackenzie's river to Florida. The field-mouse has 

 an equal range in Europe. Commerce has mingled to- 

 gether the animals as well as the plants of the old and new 

 worlds. The horse, originally from Asia, was introduced 

 into America by the Spaniards, where it was allowed to 

 run wild, and has thrived so well, that immense herds are 

 now found scattered over the pampas of South America and 

 the prairies of the West ; and in the same manner the do- 

 mestic ox has become wild in South America. Many ani- 

 mals, such as the dog, the different kinds of poultry, and 

 several singing birds, seem to be capable of living in almost 

 any climate, and are fostered and encouraged to associate 

 with man on account of the pleasure and service which they 

 afford him. Many less welcome animals have also followed 

 him, as for instance, the rat and the mouse, as well as a 

 multitude of insects, such as the house-fly, the cockroach, 

 and those which live on the. vegetables which he cultivates, 

 as the white butterfly, the Hessian-fly, &c. 



The generality of animals and plants are not, however, 

 so flexible in their constitutions. No animal, excepting 

 man, inhabits every part of the earth. Each great geogra- 

 phical and climatal region is occupied by some species not 

 found elsewhere; and each animal flourishes best within 

 certain limits beyond which it does not range. It is the 

 same with plants. Comparatively speaking, vegetable 

 cosmopolites are few in number. The greater number of 

 plants are very exacting as to the conditions of their de- 

 velopment, and will only put forth foliage, flowers, and 



