Finally kept my appointment yesterday to donate platelets at the Red Cross center in Glen Bernie yesterday, which turned out to be a lot like the prcoes sof donating plasma, except for the very uncomfortable difference of having both arms immobilized with needles and tubes. The siphoning ran about an hour and a half, with the platelets, suspended in plasma, centrifuged out, and the red blood cells returned through the other arm. Not particularly cozy, but I was treated to a private screening of Syriana, which I understood on first viewing not one bit.
But the challenge of enduring discomfort for the greater bodily good of strangers has piqued my interest, so I looked into donating marrow. Sadly, those with a history of cancer are encluded from consideration, no matter how willing the applicant is to have needles jammed into his hip bone. Not sure why this is, and I've written away to marrow.org for an explanation.