“…The use of in vitro culture is an obvious way to investigate this problem, but until the early 1 960s the majority of research workers found the culture of normal and abnormal haemopoietic cells to be very difficult (Woodliff, 1964). In a variety of systems (Woodliff, 1964;Woodliff, 1958;Woodliff, 1961;Osgood and Brooke, 1958;Lewis and Lewis, 1911;Carrel and Burrows, 1911) cells only survived a few days and showed little evidence of multiplication or differentiation.…”