One of the co-authors of 100,000,000 Guinea Pigs has written this defense of the American stomach, but by the time one finished reading it, the chances the poor stomach has seem very slim. Canned food or fresh food -- alike dangerous. Sprays poison fruits and vegetables; lax laws governing canning make canned foods a gamble. And subsidized advertising in the national magazines is an unmitigated evil. It has more fresh material --but the whole market is flooded with books of this type, and there scarcely seems room for another.