In the second half of the decade the possibility of a deficiency of a proteolytic enzyme received considerable attention from Rao and Nadler (1972 and subsequently). Some of the varied reports of CF factors and wide variety of other abnormalities, many of which other workers were unable to repeat, are described and unfortunately indicate no one was anywhere near understanding the basic defect.As Dr David Lawson had observed some years earlier – “there is as yet no wisp of smoke over the horizon of our knowledge” “we must deal with the problem as it is”.1972 Danes BS, Bearn AG. Oyster ciliary inhibition by cystic fibrosis culture medium. J Exp Med 1972; 136:1313-1317. [PubMed]