A carcinogenic compound is placed on the skin of inbred laboratory mice. In many of these mice, skin tumors develop at the site of exposure, but only months after the chemical is no longer detectable....

A carcinogenic compound is placed on the skin of inbred laboratory mice. In many of these mice, skin tumors develop at the site of exposure, but only months
after the chemical is no longer detectable. Why don’t
all the mice develop tumors, and why don’t the tumors
appear much sooner?