SGC is under attack from the goa'uld. major kawalsy has been infected when they came back from teal'c home planet. the SGC tried to operate on kawalsky thinking that once the remove the goa'uld, it would release control of kawalsky. turns out that theory was wrong. the goua'uld remained in control over kawalsky even though the doctors have removed the "snake" through surgery.
teal'c on the other hand has attracted the interests of the government and it's scientists. they seemed interested in performing experiments. teal'c an alien and they think it would be nice to cut him open.
i was hoping kawalsky would stay a little bit longer with SG1 but turns out carter was better.