Nick Haining, Rufus McLean and Sam Skinner join the party for the game at BT Murrayfield on Sunday.
Edinburgh forward Haining offers experience and versatility in the back row, while lock Skinner is in fine form, scoring two tries in Exeter’s win over Bath at the weekend.
The uncapped McLean has impressed on the wing for Glasgow Warriors in recent weeks, scoring his first try for the club.
Five players have dropped out of the squad that was picked for the postponed match with France last month.
Richie Gray, the experienced second row who impressed as a substitute against both England and Wales, misses out after sustaining a head knock in Glasgow Warriors’ recent defeat by Leinster in Dublin.
Fellow forwards Josh Bayliss, Grant Stewart and D’Arcy Rae are also absent. Bayliss, the uncapped Bath forward, was a surprise inclusion in Townsend’s last squad having previously played for England under-20s but he missed his club’s match against the Chiefs.
In the backs, stand-off Adam Hastings misses out through suspension following his red card in the Leinster-Glasgow game.
Jaco van der Walt, the Edinburgh fly-half, offers cover for Finn Russell at 10.
There is no place in the squad for centre Cam Redpath who excelled on his Scotland debut in the win over England at Twickenham but sustained a nerve-related neck injury.
The inclusion of captain Stuart Hogg will be a relief for Scotland supporters after the full-back was seen applying ice to his knee following Exeter’s win at the Rec.
Townsend has also invited youngsters Matt Currie, Rory Darge and Max Williamson to train with the national squad.
Scotland squad: Forwards: Ewan Ashman, Simon Berghan, Jamie Bhatti, David Cherry, Alex Craig, Scott Cummings, Cornell du Preez, Matt Fagerson, Grant Gilchrist, Jonny Gray, Nick Haining, Rob Harley, Oli Kebble, Willem Nel, Jamie Ritchie, Sam Skinner, Rory Sutherland, George Turner, Hamish Watson.
Backs: Jamie Dobie, Darcy Graham, Chris Harris, Stuart Hogg (c), Sam Johnson, Huw Jones, James Lang, Rufus McLean, Sean Maitland, Ali Price, Finn Russell, Scott Steele, Duncan Taylor, Jaco van der Walt, Duhan van der Merwe.