The distribution of C14 has been studied in rats following the oral administration of C14-β-carotene, which is known to be readily converted to vitamin A in the intestine. The rats were maintained in a respiration chamber and individuals removed at various time intervals up to 28 hours after dosing, and the concentration of C14 in tissues was determined. The counts per million per gram of tissue was higher in the adrenal glands and hypophysis than in the other organs examined. The pattern of C14 distribution in intestine, liver, kidneys, and blood appears consistent with current knowledge of the metabolism of vitamin A.

The excretion of silica (SiO2)n in urine and feces was determined following the oral and intraperitoneal administration of silica to guinea pigs. The urinary excretion of silica after oral administration generally reached a maximum value that was not exceeded by increasing the dose. The urinary excretion after intraperitoneal administration was considerably greater than after oral administration. The results of these experiments suggested that orally and intraperitoneally administered silica is depolymerized to the soluble form prior to excretion in the urine.

The concentration of silica in guinea pig and cow tissues was determined by the silicomolybdic acid reaction. The silica concentration was relatively low in all tissues but was greater in hair and lung than in muscle, liver, and kidney. The silica concentration of tissues was apparently not influenced by the silica concentration of the diet. The silica concentration in guinea pig and cow tissues was approximately the same.Experiments with Si31O2 indicated that orally administered silica was rapidly absorbed and excreted. The suggestion is made that silica is present both in an organic and inorganic form and that the latter is rapidly eliminated from the body.

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