In this paper, I try to extend Vygotsky's idea on artifact praxiologically. The essence of his view on artifacts lies in the concept of concrete totality of mediated activity, which says cognitive activity is beyond the individual and spreading over in the configulation among bodily actions, artifacts, and collaborative interactants. However, the notion of dialogical interaction and its analytic details are to be added to Vygotsky's view. To illustrate my extension, I conducted micro-interactional analysis on the discourse of Japanese classroom, in which children and teachers use two different social languages, i.e. standard formal Japanese and regional dialect. Changing the formation of the two social languages, children and teacher collaboratively construct the two different participation structures; one in which the floor for talk is managed formally and the other in which participants talk freely and convivially. Children and teachers uses various bodily actions including restarts, pauses, phrasal breaks, and switching of social languages, for presenting cues for changing partcipation structure and for displaying hearership.