Abstract

It is perhaps appropriate that this review has ended with a consideration of the conversion ratio. Observation of the conversion ratio requires only the simplest chemical preparation of a sample of plasma, followed by two determinations of radioactivity. Its interpretation has required a rather complicated mathematical analysis, and even this has had to be based upon certain simplifyingassumptions not fully in accord with biological facts. It is easy for observation to outdistance precise interpretation.

Yet there is reason to be satisfied with the progress which has already been made towards an orderly arrangement of the observed facts into a solid foundation of quantitative theory. With so much to build upon, further progress should be rapid. In the reviewer's opinion, future advances are likely to stem chiefly from the simultaneous use of several techniques in the detailed investigation of small groups of patients. In particular, he would urge that studies with radioactive iodine be supplemented by the determination of stable iodine not only in blood but also in urine. Many of the present uncertainties concerning quantitative aspects of iodine metabolism in man might thereby be resolved.