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.! 
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. 
