  All information about primary cosmic rays above the knee has been obtained
from results of EAS investigations. At that, two alternative approaches exist:
cosmophysical and nuclear physical. In the frame of the first one, all changes
in measured EAS characteristics are explained by the changes in energy spectrum
and mass composition of primary cosmic rays. In this paper, the second approach
is considered, in frame of which corresponding changes in EAS parameters are
explained by changes of interaction model above the knee. Some experimental
possibilities of proof of the correctness of the nuclear physical approach are
considered.
