I am Peter Hodes，a volunteer stem cell courier．Since March 2012，I've done 89 trips—of those，51 have been abroad.I have 42 hours to carry stem cells(干细胞) in my little box because I've got two ice packs and that's how long they last.In all，from the time the stem cells are harvested from a donor(捐献者) to the time they can be implanted in the patient，we've got 72 hours at most. So I am always conscious of time.
