112 THE ANALYST. R E V I E W . PLLICTICAL STUDIES IN FERMENTATION, BEING CONTRIBUTIONS TO THE LIFE HISTOI~Y OF MICRO-ORGANISMS. By EMIL CHH. HANSEN, Ph.D. (London: E. and F. N. Spon.) This work, which is a translation of the last edition of Dr. Hensen’s widely- known ‘‘ Untersuchungen ails der Praxis der Giirungsindustrie,” together with some additions, presents, for the first time in the English language, a collective ~-dss’z~~~zP of the author’s work in connection with the morphology and physiology of the fermen- tation fungi, and will in this form doubtlessly be welcomed by many who have been hitherto uuable to peruse it in the original. I t contains a summary of Dr. Hansen’s investigations into the life history of the fungoid organisnis which play such an important part in the great fermentation industries, especially in those devoted to the production of beer.Dr. Hansen dis- covered some twelve years since that differences and distinctions, quite as pronounced as in the more highly-organized plants, were to be found in these lowly organisms, and that some of the species were able to exert quite as baleful an influence on the fermentations as the bacterial organisms. This discovery led to Dr. Hansen’s great and important reform, which consisted in the introduction into fermentation operations of yeasts derived from a single cell, and therefore consisting of one species or variety only. This principle has proved itself of enormous value to all the fermentation industries; and though it was originally applied only to those engaged in the pro- duction of beer, has been extended to other branches, such as distilling, wine and cider making, the manufacture of pressed yeast, etc., and even to those, such as the manufacture of cheese and of tobacco, in which fermentations caused by bacterial organisms play an important part.Details of the various operations required for the isolation of the single yeast cell, and of cultivating from it yeast in quantities sufficiently large for practical application, are given, together with much inforiliation of a highly useful nature to the practical brewer. I n addition to this, much will be found which is of great interest to the pure scientist, not the least being the account of the author’s experiments, by means of which he has succeeded in effecting artificial variations of a more or less permanent nature in a number of the yeast fungi. Altogether, the work is one of the most remarkable of modern timeti, and is of such vast importance, that no one engaged in any of the fermentation industries can well afford to be without it. The task of translation, which has been entrusted to Dr. A. K. Miller, has been excellently performed. W. J. S. Price 12s. 6d.