THIS topic is so broad, and the need for brevity so commanding, that it seems necessary to address ourselves wholly to our subject. This means to forgo the pleasure of any individual acknowledgments to those who have worked in several laboratories; and especially of the goodly companies of Columbia co-workers, whose joint and successive researches, rather than the endeavor of any one person, have made the occasion for this recognition, and for whom as well as to whom I have the honor to express acknowledgements and appreciation. All names of persons are therefore omitted from this article. Impersonally, then, there will be reviewed here both some facts which have been found, and their significance for the establishment of a principle through which chemistry gains a new order of ability to improve life processes: not only correctively to cure illness but also constructively to build higher health and efficiency in people who are ...