EXPLANATION OF ABBREVIATIONS EMPLOYED IN REFERENCES. A. H. = Archiv für Hygiene. München. Oldenbourg since 1883. A. G. A. Arbeiten aus dem Kaiserlichen Gesundheitsamt. Berlin. Springer since 1885. A. K. = Arbeiten aus dem bakteriologischen Institut der techn. Hochschule zu Karlsruhe. Edited by Prof. Dr. L. Klein and Prof. W. Migula since 1894. = Jena. A. P. Annales de l'Institut Pasteur. Paris. Masson since 1887. H. R. Z. H. Heim Heim Lehrbuch der Bakteriologie. Second edition. Stuttgart, 1890. Kitt Kitt: Bakterienkunde für Tierärzte. Third edition. Wien, 1896. Zimmermann I and II = O. E. R. Zimmermann: Die Bacterien unserer Trink- und Nutzwässer. Chemnitz, I, 1890; II, 1894. Migula, Schiz. Migula, Schizophyta. Separate reprint from "Die natürl. Pflanzenfamilien von Engler und Prantl." Leipzig, 1896. Migula, Sys. Migula, System der Bakterien. Volume I, General = Part. Jena, 1897. Eisenberg Bakteriologische Diagnostik von James Eisenberg. Hamburg and Leipzig, 1891. Third edition. Lafar Lafar: Technische Mykologie. Volume I. Schizomycetengärungen. Jena, 1897. Günther Einführung in das Studium der Bakteriologie. Fifth edition. Leipzig, 1898. Zopf Die Spaltpilze. Breslau. Third edition. The references to illustrations in the atlas are given thus: the Plates with Arabic, the Figures with Latin numerals. Thus, 5, VIII signifies Plate 5, Figure VIII. BACTERIOLOGY. A. Introduction to the Morphology of Bacteria. 1 By bacteria (spaltpilzen, schizomycetes of Nägeli) we understand a very large group of lower vegetable organisms, morphologically very simple and uniform, but biologically extraordinarily differentiated, which are so connected with both the lower algæ1 and fungi by transition forms that a sharp separation by an accurate definition is difficult. Arthur Meyer emphasizes the relationship of the spore-forming varieties to the ascomycetes, in which the spore-forming cells appear as asci. Indeed, bacteria bear a great resemblance to the simple flagellata, which are usually conceived as animals. 2 The following definition may at least serve the practical requirements of experimental bacteriology. Small unbranched cells, rarely more than 2, hardly ever 3-5 μ in thickness, almost always without chlorophyl, spher 4 1 Recently we have learned that the green lower algæ also possess parallel colorless forms, which can be obtained from them by cultures (Beyerinck); compare also Ludwig, C. B. L. II, 348. 2 Compare Bütschli in Bronn's Klassen des Tierreiches, Bd. I, Abt. II, Mastigophora. 3 Regarding the branching forms nearly related to bacteria compare p. 19. 4 Practically, important bacteria with chlorophyl are unknown. Yet the green tadpole bacillus (Kaulquappenbacillus) of J. Frenzel must be recognized as a bacterium (Z. H. XI, 207). There is more doubt as to the relation of Dangeard's Eubacillus multisporus to the bacteria (C. B. x, 745). L. Klein described colorless varieties with bluish-green spores (C. B. VII, 440). ical, rod, thread, or spiral in form, with no organs except flagella which are used for locomotion. Vegetative increase is by transverse, very rarely by longitudinal division. A series of varieties form roundish, endogenous resting spores; in others there have been, or asserted to have been, observed conidia-like formations (arthrospores). Other means of propagation have not been observed. Bacteria occur, so far as we know, only in the following forms, which were first perfectly named by H. Buchner: Spherical form (Kugelform) (a). Oval form (Ovalform) (b): length, at most 2 × the width. Long rods (Langstäbchen) (d): length, 4-8 X width. Thread forms (Fadenform) (e). Half screw (Halbschraube) comma (ƒ): a very short segment of a screw; at most, half the turn of a screw. Short screw (Kurzschraube) (g): a short turn of a screw. Long screw (Langschraube) = spiral form (h): all screw forms possess either steep or flat turns. Spindle forms (Spindelform) (i). Oval rods (Ovalstäbchen) (k) are differentiated from the spindle form by less tapering ends, from the oval form by their greater length = 2-4 the width. Clubbed form (Keulenform) (1). Growth Groupings. Diplococcus (Doppelkugel) (m) with barely perceptible separation: Biscuit form (n). Streptococcus brevis (Kugelreihe) (o) up to 8 cocci; with barely perceptible separation : Torula form (p). Streptococcus longus (Kugelfaden)(q), or, if bent, Rosary form (Rosenkranzform) (s); with barely perceptible separation: Torula threads (r). Staphylococcus (Traubenform) (t). Diplobacillus (Doppelstäbchen) (u). Jointed threads (giederfaden) (v). Tetrad (Tetradenform) (w): plane grouping of 4, 8, 16, etc., cells. Sarcina (Würfelform) (x), cubical form: solid grouping of 8, 32, etc., cells. Branching, i. e., springing up of a side bud, was until recently unknown in connection with bacteria, and it is, at all events, rare. Besides in others, it is well established in the so-called tubercle and diphtheria bacilli as a frequent appearance, and thus it is demonstrated that here forms occur which do not strictly belong to bacteria. Exceptionally, true branching appears to occur in other varieties. Heim mentions it in Bact. fluorescens. Vincenzi (C. B. XIV, 149) appears to have observed the same in tetanus, but in spite of special care, we have made no similar observations. Often pseudodichotomy is confused with branching and dichotomy. According to Babès (Z. H. xx, 412), it occurs not infrequently in the most typical bacteria, and consists in this, that either the lower member of a thread grows past the side of the upper member, or that, in a row of cocci, the division of a coccus parallel to the direction of the string suddenly creates the beginning of a second thread. Stolz (C. B. XXIV, 337) has recently studied exhaustively 1 Some authors falsely designate this true branching as true dichotomy, but true dichotomy means, according to botanical usage, only the division of the growing ends of threads into two equal twigs, and it is not certainly known to occur in bacteria. and represented this abnormal division in streptococci. It occurs very frequently; indeed, we have often seen it. Regarding the structure of the bacterial cell, much has been recently written. I must limit myself to what seems to me the most probable. According to Alfred Fischer,1 the conditions are very simple (Fig. 3): The bacteria consist of a cell-membrane, a protoplasmic layer, and a central fluid. Regarding a nucleus see below. In saline solutions (sodium chlorid, potassium nitrate, etc.) there occurs, the more concentrated Fig. 2.-Pseudodichotomy: a, In bacilli; b, in streptococci. GDCD GDADAD Protoplasmic layer. Spaces filled with cell-juice. Fig. 3.-Bacillus oxalaticus Migula (after Migula). the solution the more rapidly, through abstraction of water, a "plasmolysis,"-i. e., a contraction of the mass. of protoplasm with partial separation from the cell-membrane. 2 Thus are explained many clear vacuoles which occur in an ordinary cover-glass preparation of many bacteria (for example, B. typhi), and which were formerly 1 Untersuchungen über Bakterien, 1894. Berlin. Separatabdruck aus den Jahrbüchern für wissenschaftl. Botanik, XXVII, Heft 1; and Untersuchungen über den Bau der Cyanophyceen und Bakterien., Jena, 1897. 2 Frequently the drying on the cover-glass is sufficient to produce a picture of plasmolysis. |