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reactions are summarized by II Jenseii and Leon E . Tenenbauni. h close physiological interrelationship seems to exist betxeen hormones, enzymes and vitamins. However, our present knowledge of the mechanism by 15 hich the various endocrine principles may affect enzymatic reactions is rather meager and does not permit any definite conclusions. The use of absorption spectra in the study of vitamins. hormones, and coenzymes has become an important too1 for determining the concentration. structure, and identity of these compounds. The fundamentals underlying the absorption phenomenon as n-ell as its nunierous applications are discussed by Wallace 11 Hrork
ERWXHAAS. C o l u ~ i u ~ l ; iDetermination c of Traces of M e t & . BY E. U . BASDELL. T e n York: Interscience Publishers, Inc., 1944. Dr. Sandell has earned signal applause for this new book on quantitative analysis. He has lifted the term “trace” froni a limbo of ambiguity and attempted to furbish it to a degree which will justify its use in scientific language. .Z trace has often been an expression of the analytical chemist’s limitations, or the deus ez machina by which vagaries of catalytic or medicinal properties, reaction rates, or the fundamental properties of color, taste, odor, etc. could be plausibly explained. When one considers the many vast fields-metallurgy, agriculture, nutrition, etc.-in which i t is imperative to give precision t o the meaning of “trace”, one can realize \
