196 
ON THE GEOOEAPHICAL 
of vegetables from one country to another ; and, by cul- 
tivation, he has so changed the face of nature which sur- 
rounds him, that the surface of the earth has, in some 
measure, lost its primeval features, and vegetation, at 
least, has experienced great modifications. Most animals 
have the means of spreading themselves on the surface of 
the globe. The element which saw their birth, offers no 
limits to marine animals. Certain mammals extend, con- 
stantly, the sphere of their habitation, and spread them- 
selves by degrees over many parts of the world. Other 
species accompany man in his peregrinations, even beyond 
seas, dispersing themselves in diverse regions, either when 
transplanted by man himself, or when, recovering their 
liberty, they form, as it were, colonies far from their 
mother country, where it sometimes happens that their 
race is totally destroyed, or that all the individuals have 
passed to the domestic state. Birds enjoy more than other 
animals the faculty of moving from one place to another ; 
the element in which they move nowhere presenting obsta- 
cles to them, a large part of the inhabitants of the air lead 
a real nomade life, and often establish themselves in places 
where they were never seen before ; a great number dis- 
perse themselves, in their periodic migrations, into coun- 
tries the most distant, and become true cosmopolites ; the 
same species inhabiting, at the same time, all parts of the 
earth. It is far otherwise with Hep tiles. None of the 
circumstances we have mentioned can be rigorously ap- 
plied to these animals. Deprived, for the most part, of 
the means of performing distant journies, they are, in 
some measure, attached to the soil which gave them birth ; 
and we do not recognise in them any instinct to flee the 
natal soil, when certain circumstances would seem to de- 
mand it. The cold which deprives them of the means of 
subsistence, causes them at the same time to fall into a 
profound lethargy ; and Nature, in this simple manner, 
cratches over their preservation during the winter. Man 
entertains an aversion for these animals, some of which 
are noxious, it is true, but many of them are innocuous, 
and even useful ; he repels them all, and seeks not to 
tame them ; still less is he inclined to transplant them. 
