After inducing experimental fluorine poisoning in two groups of young rats by oral administration of various NaF aqueous solutions consecutively for one week in one group and for one month in another group, the author observed changes in the phosphorus metabolism of teeth and bones of these animals by means of radioactive isotope p(32); and obtained the following results. Method: As for the source of P(32), phosphoric acid in the form of H(3)P(32)O(4) was used. Forty-eight hours after a single intraperitoneal injection of 0.2 mc/kg P(32) these rats were sacrificed, and then extracting teeth and bones and weighing them to an exact 0.1 g dryweight each, these were pulverized and sedimented. After filtering and drying the sediments, the radioactivity was determined by Geiger-Müller counters. The specific activity of P(32) was calculated on the basis of the radioactivity and quantitative determination of phosphric acid. Experimental results: 1. In the group administered with NaF for one week the specific activity of P(32) incorporated in the teeth tended to decrease along with the increase in the volume of NaF administered. However, when the volume of NaF administered was small (as 2.5 mg/kg), a slight increasing tendency in the specific activity could be observed as compared with the control.
2. The specific acitivity of P(32) incorporated in the bones of the same group showed rather an increasing tendency along with the increase in the volume of NaF administered. 3. In the group administered with NaF for one month the specific activity of P(32) incorporated in the teeth tended to decrease along with the increase in the volume of NaF given. 4. The change in the specific activity of P(32) in the bones of the latter group was less marked when compared with that in the teeth. 5. In the latter group the amout of P(32) incorporated in epiphyses was found to be greater than that in diaphyses.