Board Thread:Warhammer 40k General Discussion/@comment-5702034-20131128193249/@comment-3258762-20131128200124

The Apothecaries make extensive screening of the aspirant to see if their bodies will accept the organs, and is done before they are made into scouts. This is what happened to the Crimson Fists senechal (Can't remember his name) who was the top aspirant and would almost definately have become accepted as a Scout Marine, only to have his hopes dashed as the Apothecary told him his body would not accept the implants and, I quote: "You will never be Astartes."

He, in his dispair, was given the chance to serve his Chapter by Pedro Kantor by basically being the boss of the serfs.

However, this all varies depending on the Aspirant and the Chapter. For Space Wolves, failure is not tolerated; You succeed or you die...or become a Wulfen. For more lenient chapters, the aspirant may serve in the defensive force, whilst, say, the Iron Hands would probably make them into servitors.