Each volunteer will be studied 3 times, the order of which will be determined randomly by computer. Participants will report for the study at the Division of GI Surgery (E−floor, West Block, Queen's Medical Centre), at 7:15am. On arrival the subject's height and weight will be recorded and 'drip needle' will will be placed in the back of the wrist. The hand will be rested in a hand−heater allowing venous blood to be sampled.