186 THE KINGDOM OF MAN 



variety than in any other part of the world is due to the 

 sudden introduction, by means of some geological change, 

 of a deadly parasite which spread as an epidemic and 

 / extinguished the entire horse population. 



Whatever may have happened in past geological 

 epochs, by force of great earth-movements which rapidly 

 brought the adaptations of one continent into contact 

 with the parasites of another, it is quite certain that 

 man, proud man, ever since he has learnt to build a ship, 

 and even before that, when he made up his mind to march 

 aimlessly across continents till he could go no further, 

 has played havoc with himself and all sorts of his fellow- 

 beings by mixing up the products of one area with those 

 of another. Nowhere has man allowed himself let 

 alone other animals or even plants to exist in fixed local 

 conditions to which he or they have become adjusted. 

 With ceaseless restlessness he has introduced men and 

 beasts and plants from one land to another. He has 

 constantly migrated with his herds and his horses, from 

 continent to continent. Parasites, in themselves beneficent 

 purifiers of the race, have been thus converted into terrible 

 scourges and the agents of disease. Europeans are 

 decimated by the locally innocuous parasites of Africa ; 

 the South Sea islanders are exterminated by the compara- 

 tively harmless measles of Europe. 



A striking example of the disasters brought about by 

 man's blind dealings with Nature disasters which can 

 and will hereafter be avoided by the aid of science is to 

 be found in the history of the insect phylloxera and the 

 vine. In America the vine had become adjusted to the 

 phylloxera larvae, so that when they nibbled its roots the 

 American vine threw out new root-shoots and was none 

 the worse for the little visitor. Man in his blundering 

 way introduced the American vine, and with it the 



