Our local Red Cross chapter called recently to ask if we’d donate some blood platelets.  Since we had some left over, we said “sure.” To get the platelets, a machine whirls the blood around in a centrifuge, as a tube in one arm sends blood to the machine and one in the other arm receives blood back from the machine (sans some of the platelets, we assume.)  The whole process takes about two hours or so.  501 more words