92 DOMESTICATED ANIMALS AND PLANTS 



animal with great skill and at once ripping up the body with 

 the teeth and tusks. 



In domestication 'we change all this. We shut him up in 

 a close little pen in the open sun, away from water, and feed 

 him mostly on grain, or, in cases of extra care, on mush, perhaps 

 cooked and steaming hot. Now the pig cannot sweat. He has 

 no glands for the purpose. In nature he lives in the shade and 

 runs to the river when oppressed by heat. He is not used to an 

 exclusive diet of seeds, and has never accustomed himself to 

 hot soup and steaming mush. He has not been selected on 

 that basis, and what wonder that he makes the most of any water 

 or even mud that he can reach, doing his best with snout and 

 tusk to bury himself in the ground, and snapping greedily at 

 alfalfa or clover hay pasture grass, or anything else that will help 

 to restore the conditions to which he had been accustomed by long 

 generations of selection ! We must either change our habits of 

 keeping the pig, as the best farmers are doing, or he will be 

 obliged to radically change his nature, which will take much time 

 and be exceedingly expensive to us, for it costs dearly to make 

 over a species in respect to fundamental characters. 



Again, we often add a requirement or two to the natural 

 qualities which led to domestication, all of which will of course 

 require no little readjustment of the nature of the species in 

 order to meet new demands. For example, the chicken was 

 doubtless domesticated for her eggs and the sheep for its wool, 

 but we have made meat animals out of both. Beets were at first 

 cultivated as a toothsome vegetable, but later developed for the 

 sugar content, which vastly changed the nature of the plant, as 

 it required substantial addition to the leaf surface. 1 



So examples might be multiplied indefinitely to show how 

 we have added, and indeed are constantly adding, new require- 

 ments to our domesticated species, requiring additional selection, 



1 Sugar is practically carbon and water, and this new demand fell heaviest 

 on the leaves, which, as has been explained, are the agents for fixing and bring- 

 ing into the plant the carbon from the carbon dioxide of the air. 



