Abstract
The free inositol contents of the tissues of the rat, guinea pig and rabbit were measured by a microbiological-assay method. The highest concentrations were found in the thyroid and pituitary glands of all species. In homogenates of these glands in the rat, the inositol was exclusively located in the cytoplasmic fraction obtained by centrifuging. In the organs of all species the concentration of free inositol was much higher than that found in the plasma. The free inositol content of the rat mammary gland increases markedly during lactation. The concentration in the blood plasma and kidney falls slightly after parturition, but that in the liver does not change.