A physicist's interpretation of some aspects of vitamin B12 metabolism and its use to routinely estimate total-body B12.

S FOR TECHNOLOGISTS' SCIENTIFIC PROGRAM 474 AUTHOR INDEX 484 CALENDAR 488 PLACEMENT LXII EDITORIAL COMMUNICATIONS. All •ditorialcorr.spond.nc should b sent to the Editor, B.lton A. Burrows, M.D., 720 Harrison Ave., Boston, Mass. 02118, Phone 617-262-4474. Books and monographs covedng the use of nuclear phenomena in the diagnosis and trotment of diseas and allied fields will be reviewed as space is available. Send copies to the Editor at the address above. BUSINESS COMMUNICATIONS. Send all correspondenceconcerning business (advertising, subscriptions, change of address, etc.) to the publisher, Society of Nuclear Medicine, 211 E. 43rd St., New York 10017, Phone 2@2-687-9169. Advertising rates are available from the publisher. Advertising is accepted subject to approval by an editorial committee. Forms close on the 20th of the second month preceding date of issue. June, 1971, Vol. 12, No. 6. Second Class postage paid at New York, N.Y., ., and at additional mailing offices. Subscription rates are $30 per year within the United States; $31 in Canada and South and Cenfral America; $35 elsewhere (includes air mail postage). Student subscription $@8. Single copies $3; foreign $3.25; convention issue (June), $5. Subscriptions on a calendar-year basis. Remittances should be made by check, draft, post office or express money order, made payable to Society of Nuclear Medicine. Notify the Society of change of address at least 30 days before date of issue by sending both the old and new address. Published monthly at 211 E. 43rd St., New York, N.Y. 10017. f@ Society of Nuclear Medicine, June, 1971. Society of Nuclear Medicine, 211 E. 43rd St., New York, N.Y. @0017. Postmaster: Send form 3579 to 211 E. 43rd St., New York, N.Y. 10017.