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This will acknowledge' receipt of your recent letter. I will attempt to test the combinations mentloned as rapidly as the press of other projects permits. I wlll be somewhet hampered in reproducing the exact conditlons of the experiments, since I have so few subjects who respond strongly to doses as low as those mentioned. As you know, I already had adrenergic biocking agents In mind and hed been considering trying Rigitine.

Toleronce experlment:s are proceeding well. I have found that doubling the dose restores the mental effects oniy partlally, and next week I intend to trlple It. This. will mean that one of the' patlents wlll be recelving from 3 to ó microgrems per kilogrem, and in one Instance the total dose will be 390 microgrems.

I will look forward to seeing you in luly.

Very sincerely yours,

Harrls Isbel!, M.D Director of Research

DEPARTMENT OF TH, EDUCATION, AND WAR CY

IN REPLYING, ADORESS THE

PUBLIC HEALTH SERVICE Addiction Research Center Lexington, Kentucky 18 June 1954

Daclassified FEP 97713875 date