420 
DIGESTIVE ORGANS AND FOOD 
foods are many biological problems of great importance. 
Several of these have been mentioned from time to time in 
the sections devoted to zoology and botany. Numerous 
insects feed upon our growing crops, and as the acreage 
increases, more food is furnished for these same insects, 
until the damage done by them amounts to millions of 
Figure 376. — A Typical Western Wheat Field. 
The ripe grain is being cut by a self-binding reaper. The bundles of 
wheat are set up into shocks or stooks of about twelve bundles each. 
Here they must remain until the grain dries, which takes about one week in 
good weather, after which it can be threshed. Photograph furnished by 
the Omaha Chamber of Commerce. 
dollars annually. It requires all of man’s skill to prevent 
them from destroying some crops. 
Not only are animals destructive to the grains and fruits 
but many fungous diseases attack these same groups of 
plants and kill them or prevent them from producing a good 
yield. Again, all animals must have their food manufactured 
for them in just the same sense that man does; so that man 
