THE OPTIMAL TEST DOSE IN TUBERCULOSIS RESEARCH

To the Editor:—  It would be desirable to obtain an unassailable degree of protection against human tuberculosis. But how much are we willing to accept, at a time when BCG, good diagnosis, segregation, rest in bed for a year, collapse therapy, adequate vitamin intake and the intriguing but elusive prospect of drug or enzyme therapy are just about all that we have established in this field?The chronic disease itself is intrinsically and indirectly just as great a problem as the actual number of deaths it causes. Most human tuberculosis is not fatal, though it spreads in house-holds and institutions and may cause great misery and economic loss. The recognizable disease is but seldom contracted by a casual infection, in the street car or subway, but usually by several subfatal doses in a dwelling permeated with infection.From these facts it follows that significant protection against even 1 minimum lethal