Cuthbert is a big defender and is exactly what we need, especially with Mark McAusland and Will Haining missing Saturday's game. He has previously had a spell on loan with Livingston, but his first league game for Saints will be his first match in the SPL.
This should be a decent signing - you don't captain Celtic's reserve sides and represent Scotland at numerous levels if you're rubbish - and gives us much needed cover at the back.
Cuthbert is likely to be Saints last signing of the summer.