In six subjects with normal serum‐B12 level the liver B12 was about 1 μg per gram liver tissue wet weight. In the livers of eleven subjects with B12 deficiency the B12 content was only one fourth to one fiftieth of the normal amount. Methyl‐B12, deoxyadenosyl‐B12 and hydroxo‐B12 were demonstrated in control livers by the chromatographic‐bioautographic technique. Deoxyadenosyl‐B12 was the major component. The liver methyl‐B12/deoxyadenosyl‐B12 quotient was increased in four of seven subjects with vitamin B12‐deficiency.

A study of the absorption of vitamin B,, labelled with 67Co was performed by whole-body counting. The subjects were measured in prone and supine positions by a NaI(T1) scintillation detector which moved l50 cm along the subject. The technique was evaluated by model studies, by whole-body counting of subjects and by radioactivity assay of excreta. The influence of body size upon the whole-body counter sensitivity was demonstrated. This influence was considerably diminished when the Compton energy range instead of the photopeak energy range was used for the determination of the radioactivity in the body.

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