254 DOMESTICATED ANIMALS 



with the coming of man, the species which by its swiftly 

 progressive desires has become a host in itself, a disturbing 

 element was introduced into the old order. Man as a primi- 

 tive savage falls into the natural system without greatly dis- 

 turbing it ; but man as a soil-tiller, in so far as he carries out 

 his subjugative work, utterly wrecks the ancient establish- 

 ments of life. To attain his object he has to banish from the 

 soil nearly all the plants which originally belonged upon it, 

 and in their place, with or without intention, he introduces 

 species from other organic provinces. With the change in 

 plant-life necessarily goes a like, or even a greater, alteration 

 in the native animals. They are driven into the wilderness 

 or, it may be, extirpated. The reader who would obtain an 

 idea of these changes will do well to study the invasions of 

 weeds or of those noxious insects which in the economy of a 

 civilized country may be likened to weeds. These pests are 

 in nearly 'all cases invaders which owe their successes to the 

 fact that our treatment of the regions they have entered has 

 opened vacancies in the once closed ranks of the indigenous 

 host, into which the foreigners are free to enter. In the 

 fresh field they are not likely to find enemies which by long 

 training are especially fitted to cope with them, and so they 

 run riot and contest with man the gains he has won from the 

 ancient possessors of the land. 



Of all the large questions which the consideration of the 

 future of man's work on this planet opens to us, there is none 

 which now appears to be more serious or, in its consequences, 

 more far-reaching than this concerning the treatment which 

 he is to give to the old natural order of sea and land. The 

 very first condition of civilization is an utter spoiling of that 

 order, so far as the land areas are concerned, in the fields of 



