Bees boss Uwe Rosler has moved for the 33-year-old former Watford and Birmingham centre-half after watching his side go down 4-0 at Bradford last weekend.
"Martin has a bunch of experience. He is a big unit," Rosler told the club website.
"Bradford showed that we need someone who can kick the ball and head it away and lead other players around them.
"It is worthwhile for us to get someone with Martin's experience on loan and both parties can see where we are after that has finished."