Abstract
The concentrations of vitamin B12 in certain organs of the male rat were studied under conditions where the animal was deficient in the vitamin and where it was fed ample quantities. The kidneys stored large amounts when an abundant supply was available. The pituitary and the adrenals also contained high concentrations, equal to or not far below those in the kidneys of vitamin B12-deficient rats but much less than those in the kidneys of vitamin B12-sufficient rats. The heart contained fair amounts when the vitamin was supplied. The other tissues studied contained much smaller concentrations, the testes and seminal vesicles having particularly low amounts when the rat was deficient in the vitamin. Rats aged 189 to 301 days differed little from those aged 62 to 77 days of age in respect to the vitamin B12 concentration in their tissues, except for slightly greater storage in a few of the tissues in the older group when the vitamin was administered.