p. 10 writes appreciatively: "Hansen by the use of the pure culture becomes the reformer in the science of yeast organisms, as Koch was in that of bacteria". The object of his book, however, consists in substituting in several places other methods in place of those introduced by Hansen; methods, viz., which more resemble those of Koch. In it, he attacks several points in Hansen's work in that direction which have been defended by Alfr. Jörgensen and Will. The latter says (Zeitschr. f. d. ges. Brauw., 1899, p. 612): "The pioneer researches of Hansen have brought about a complete revolution in this direction. The extension of Pasteur's study of the organisms which produce diseases in beer, by Hansen, who showed that diseases are also produced by yeast species, and the building up of this theory by the latter investigator, his pupils and the zymo-technical laboratories, have advanced to such a point, that to-day we can with comparative quickness and certainty, by characteristic appearances, recognise all those organisms, in particular those yeasts, which are foreign to a normal yeast or fermentation and consequently also to a normal beer." Will and Jörgensen themselves have contributed. Among others, Prior's laboratory also took up Hansen's analytical methods. The latter depend in general on the study of important and characteristic physiological functions, but morphological characteristics were also included where this was possible. The same analysis can, of course, in many cases be performed in different ways. There is room enough for other methods besides those given by Hansen.

For illustrating the progress of the development it is instructive to go through various successive editions of textbooks and handbooks of the fermentation industries, e.g., such works as that of Thausing mentioned above. Even at the beginning of the eighties no mention is made of a reform with regard to the yeast question; but in the following years Hansen's ideas make themselves increasingly felt.

As regards the pure culture system in wine manufacture, see Wortmann's book, "Die Anwendung und Wirkung reiner Hefen in der Weinbereitung," Berlin, 1895. On the pure culture system in spirit and pressed yeast manufacture, see Delbrück and P. Lindner in the "Zeitschr. f. Spiritusindustrie," and "Wochenschr. f. Brauerei," 1892 and 1895.

Although a large part of Hansen's investigations deals with the study of species, and although they depart from new points of view and have given rise to important progress, systematic botany has hitherto paid little or no attention to them. Descriptive botanists repeated substantially the methods of description of Reess, and proceeded from the old fallacy that a microscopical investigation is sufficient to distinguish the systematic units from one another. It is still more unfortunate that such a doctrine is taught in more than

one of the Technische Hochschulen. The theoretical aspects of Hansen's research received special recognition in mycological textbooks (e.g., Zopf's Die Pilze, 1890), and in those of the chemistry of fermentation (e.g., Bourquelot, 1889; Langer, 1890; Ad. Mayer, 1895; Prior, 1896). It has introduced a new chapter into this literature.

XX.-LINTNER, CARL: Über Malz und dessen Einfluss auf die Haltbarkeit und Güte des Bieres. (Zeitschr. f. d. ges.

Brauw., 1880, p. 384.)

XXI. KOCH, ROBERT: (1) Zur Untersuchung von pathogenen Organismen. (Mitt. aus d. Kaiserl. Gesundheitsamte, Bd. i., 1881, p. 1.)

(2) According to Hueppe, the important plate culture was first demonstrated on the occasion of the Hygiene Exhibition in a lecture given by Koch during the XI deutschen Ärztetage, 1883, at Berlin. Special directions for these cultures were first published by Biedert in the Deutsche Medicinal-Zeitung, 1884.

XXII.-THAUSING, JULIUS: Einfluss der Hefegabe auf Hauptgährung, Hefe und Bier. (Allg. Zeitschr. f. Bierbrauerei, 1884, p. 872.)

XXIII.-FISCHER, EMIL (1) Die Chemie der Kohlenhydrate und ihre Bedeutung für die Physiologie. Berlin, 1894.

(2) Einfluss der Konfiguration auf die Wirkung der Enzyme. (Ber. d. deutsch. chem. Ges., Bd. xxvii., 1894, and xxviii., 1895.)

XXIV. DELBRÜCK, MAX: Lecture.

(Wochenschr. f. Brauerei,

Bd. xii., 1895, No. 30, pp. 732-733.)

XXV.-BUCHNER, EDUARD: Fortschritte in der Chemie der Gärung. Tübingen, 1897.

SECTION II. (Pages 16 to 169).

1. Text-Books, Handbooks and Journals.

DE BARY, A., and WORONIN, M.: Beiträge zur Morphologie und Physiologie der Pilze. 2. Reihe. Frankfurt, 1866.

BEHRENS, W.: Tabellen zum Gebrauch bei mikroskoipschen Arbeiten. Braunschweig, 1898.

DIPPEL, L. Das Mikroskop und seine Anwendung. Braunschweig, 1882.

FRIEDLÄNDER: Mikroskopische Technik. Bearb. v. Eberth. 6. Aufl. Berlin, 1900.

HUEPPE, F. Die Methoden der Bakterienforschung. 5. Aufl. Wiesbaden, 1891.

JÖRGENSEN, A.: Die Mikroorganismen der Gärungsindustrie. 4. Aufl. Berlin, 1898.

LAFAR, F. Technische Mykologie. I. Schizomyceten-Gärungen. Jena, 1897.**

LINDNER, P. Mikroskopische Betriebskontrolle in den Gärungsgewerben. Berlin. 1 Ausg., 1895; 2 Ausg., 1898.

LINTNER, C. J.: Handbuch der landwirtschaftl. Gewerbe. Berlin, 1893.

Considers the application of the pure culture system not only in breweries, but also in distilleries and in pressed yeast manufacture.

MORITZ and MORRIS: A Text-book of the Science of Brewing. London, 1891.

STRASBURGER, E.: Das botanische Practicum. Jena, 1887.

SYKES, W. J.: The Principles and Practice of Brewing. London, 1897.

References to the pure yeast system in English top fermentation breweries.

Centralblatt für Bakteriologie, Parasitenkunde und Infektionskrankheiten. 2. Abt. Herausg. von Oscar Uhlworm and

Emil Chr. Hansen. Jena, 1895 f.

Jahresbericht über die Fortschritte in der Lehre von den Gärungsorganismen. Herausg. von Alfr. Koch. Braunschweig, 1891.

Zeitschrift für wissenschaftliche Mikroskopie. Herausg. von W. J. Behrens. Braunschweig, 1884 f.

2. Special Works.

BREFELD, O. Methoden zur Untersuchung der Pilze. (Ber. d. med.-phys. Ges. zu Würzburg, 1874; also in Landwirtsch. Jahrb. Bd. iv., 1875.)

Botanische Untersuchungen über Schimmelpilze. Parts 2 and 4, 1874 and 1881.

The above researches are specially important as regards methods of studying morphology and life history.

GREG, P. H. Fermentation in Rum Distilleries. (The SugarCane. Vol. xxv., 1893, No. 292.)

HANSEN, EMIL CHR.: Contributions à la connaissance des organismes qui peuvent se trouver dans la bière et le moût de bière et y vivre. (Compt. rend. des travaux du laborat. de Carlsberg, Tom. i., livr. ii., 1879, p. 49.)

Sur le Saccharomyces apiculatus et sa circulation dans la nature. (Ibid., Tom. i., livr. iii., 1881, p. 159.)

Recherches sur les organismes qui, à différentes époques de l'année, se trouvent dans l'air, à Carlsberg et aux alentours, et qui peuvent se développer dans le moût de bière. (Ibid., Tom. i., livr. iv., 1882, p. 197.)

Here also are found the principles of Hansen's spore analysis (p. 206) and his first pure culture method (p. 212).

Les ascopores chez le genre Saccharomyces. (Ibid., Tom. ii., livr. ii., 1883, p. 13.)

On p. 23 and following there is a somewhat more detailed description of Hansen's pure culture methods and of his spore culture method.

Über Wiesner's neue Prüfungsmethode der Presshefe. (Dingler's polytechn. Journal, 1884.)

Méthodes pour obtenir des cultures pures de Saccharomyces et de microorganismes analogues. (Compt. rend. des travaux du laborat. de Carlsberg, Tom. ii., livr. iv., 1886, p. 92.)

A detailed description of the manipulations in his pure culture methods.

HANSEN, EMIL CHR: Les voiles chez le genre Saccharomyces. (Ibid., Tom. ii., livr. iv., 1886, p. 106.)

Untersuchungen aus der Praxis der Gärungsindustrie, Heft 1, 1. Ausg., 1888; 3. Ausg., 1895, Heft 2, 1892. München und Leipzig.

The contents of Part 1 are as follows: 1. The pure culture of methodically selected yeasts in the service of the industry. 2. Studies of yeast species. 3. On the practical testing of beer in lager casks, with respect to its stability. Part 2 contains: 1. The technical analysis of the micro-organisms of air and water. 2. What is Pasteur's pure yeast? 3. Investigations on diseases caused in beer by alcoholic fermentation fungi. 4. On the present-day use of my pure yeast culture system.

The majority of the above works are to be found in Danish, with résumés in French, in the journal of the Carlsberg laboratory. Also the English edition mentioned above, London, 1896.

Sur la vitalité des ferments alcooliques et leur variation dans les milieux nutritifs et à l'état sec. (Ibid., Tom. iv., livr. iii., 1898, p. 93.)

Methods are given here for preserving pure not only yeast species, but also alcoholic fermentation fungi in general.

Neue Untersuchungen über die Sporenbildung bei den Saccharomyceten. (Centralbl. f. Bakt., Par. u. Inf. 2. Abt., Bd. v., 1899, No. 1.)

La variation des Saccharomyces. (Compt. rend. des travaux du laborat. de Carlsberg, Tom. v., livr. i., 1900.) HOLM, J. CHR.: Sur les méthodes de culture pure et, spécialement, sur la culture sur plaques de M. Koch et la limite des erreurs de cette méthode. (Compt. rend. des travaux du laborat. de Carlsberg, Tom. iii., livr. i., 1891, p. 1. In German in Zeitschr. f. d. ges. Brauw., 1891, S. 458.)

Analyses biologiques et zymotechniques de l'eau destinée aux brasseries. (Compt. rend. des travaux du laborat. de Carlsberg, Tom. iii.,livr. 2, 1892, p. 107.)

HOLM, J. CHR., et POULSEN, S. V.: Jusqu'à quelle limite peut

on, par la méthode de M. Hansen, constater une infection de "levûre sauvage" dans une masse de levûre basse de Saccharomyces cerevisia? (Compt. rend. des travaux du laborat.