(Above). One unit of Haas’ dialyser. Several such units could be employed, as in the young woman being dialysed in 1926 by Haas using 3 such units in series (below). Blood was withdrawn from the patient into the dialyser, allowed to equilibrate then re-allowed to flow back into the patient. This form a “fractional” dialysis was used in his first experiments by Kolff, and in some dialyser designs into the 1950s [1]. (courtesy Dr Jost Benedum)