  It is argued that directed flow $v_1$, the observable introduced for
description of nucleus collisions, can be used for the detection of the nature
of state of the matter in the transient state of hadron and nuclei collisions.
We consider a possible origin of the directed flow in hadronic reactions as a
result of rotation of the transient matter and trace analogy with nucleus
collisions. Our proposal it that the presence of directed flow can serve as a
signal that transient matter is in a liquid state.
