Who is Janus from Selected Poems and what is their importance?

Janus appears in the poems, The Self and the Other, The Gold of the Tigers and The Maker. He is the two-headed, Roman god of doorways, beginnings, and endings. His faces could see into the past and the future. Borges uses Janus as a symbol of the duality of nature and man, and of the past and future. He likes that Janus' two faces look away from each other.