Heaft.@ Servic Pul a'. ,Dep*' I.. Of HEALTH, EDUCATION/ AND LRAR* NATIONAL INSTITUTES OF HEALTH IN 019PLYING AC*Itt$S T"g 8 March 1957 MATI*n,%I. ist.%Tmlrt of MiliTAL HCALTIF ADDICTION RISCARCH CIIITER U.S. FUSUC HILALTH SGRVICI HOS?TYAL P. 0. Box 2000 L=iN4=oi. Kgnncxy have tested the new lot of material an 3 men using to I .5 A ./2kg. of body we Ight- . Typical doses of I re actions a ope ared wh I ch were of the s aMZL Intensity observed in the same patient s dur Ing, a pre ced tng week, using a lot of o I der mate r I a I fherefore, foal that the new mat'erlal is biologically active as the old, and that any further testing of if Is unnecessary. If you wish more ex2tens lve -testing please let me know. I am enclosing a table showing resul@s obtained when 2-4 mg./70 kg. of BL)L-148 were administered si..-nuitaneoLs ly with .5-1 .5 mcg./kg. of LSD. There is, obvious ty, no statistical difference In any of the measurements. I have ob2toined a copy of Nature containing the paper by Ginzel and Mayer-t'-7ross- in which blockingl of LSD-25 by 6(;-L was reported. This apparently occurred only when BCL.was given for @t least f%-.,o days prior to LSD. I -wltl I oroceed to in,,cs@, '-afe fhls If sounds more 2 like tolerance than it does like eompetitive blocking. s injec4,,.Ion of Bt@L Others also report that lntravenou at -the heig.hfl of -'the reaction, di-d n-o t a I f.e. r t he L SD- .redction. Very sincere ly yours, 3 o, Harris ls'oe 11 .9. Me De Director H I w Enclosure