When a text-book has run through six editions in a few years its place as a standard may be regarded as established. Halliburton's "Essentials of Chemical Physiology" is exactly what its title proclaims it to be; the essentials of the subject are considered systematically and concisely, while clearness of exposition is not sacrificed to brevity. In this latest edition the author has added, with much discretion and good judgment, the most important recent advances. If the student uses this book as a basis for his study of physiologic chemistry, and does a proper amount of collateral reading from more extensive treatises, he should secure a good understanding of the subject; the danger is that with such a compact little epitome as this he will be content with its contents and fail to seek wider sources of information. We may add a particular word of approval of the expression "chemical physiology,"