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) (8); 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, the conditions are very simple (Fig. 8); 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 % Pudodichotomy: a, In bacilli; b, in streptococci. 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 '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. looked upon as spores. (Compare Fig. 4, a, b, c.) In water, this shrinking rapidly disappears, and also under the prolonged action of saline solution. Migula (A. K., Bd. 1), simultaneously and independently, reaches the same opinion as A. Fischer regarding the very large Bacillus oxalaticus, a spore-forming variety related to the hay bacillus. It happens especially in this that in the pressing outward of the protoplasmic layer, the central fluid space becomes distinct; in dehydrating media it becomes smaller; in water, larger. While the botanists have hitherto sought in vain for a true nucleus, Arthur Meyer would recognize it in small, single, oval granules, staining with Ruthenium red and potassium iodid (Flora, 1897, Band 84, 185). Compare also the hitherto scarcely studied observations of A. Wagner (C. B. xxiii, 433), according to which nuclei were easily stained by primulin and hot Bordeaux red. In the interior of bacterial cells there are found, after proper staining, very many varieties of peculiar granules, which Babes, who discovered them, named metachromatic bodies (i. e., staining differently from the cell-body). Ernst, the first accurate investigator of these bodies, called them nuclei or sporogenic granules. While I refer to the literature of Babès (Z. H. xx, 412), which is rich in controversy, I give only the seductively clear view of one of the latest investigators of the subject, R. Bunge. Bunge (Fort. der Med., XIII, 813 and 853) distinguishes : 1. Ernst's granules. They stain blackish-blue when treated with warm Löffler's methylene-blue, washed in water, and after-stained with Bismarck brown. These granules are entirely absent in many spore-forming varieties (anthrax, megatherium), and in others it can be shown that they have nothing to do with spores. They are therefore granules of unknown rank. 2. Antecedents of spores (Bunge's granules). Small granules, usually occurring multiple in sporulating cells, not staining according to Ernst's method, but, on the contrary, in boiling Löffler's solution. They are best shown, after previous treatment of the dried preparation with chromic acid, sodium peroxid, or hydrogen peroxid, according to the ordinary spore staining. (See Technical Appendix.) The perfected spores are formed by the union of many small antecedents. Bunge explains the controversy which has occurred as due to much confusion regarding the two varieties of granules. Regarding the cell-membrane, it is especially to be remarked that it often appears somewhat swollen, and not sharply outlined from without. In many bacteria ("capsule-bacteria" of authors) the thickening of the membrane or its outer layer is so extreme that the bacteria appear Bacterium pneumonia Bacillus anthracis (Friedländer). (Cohn). Streptococcus lanceolatus (Gamal.). Fig. 5.-Capsule-formation (schematic). surrounded by a true mucous envelope or capsule, which is distinguished by its slight staining property with anilin dyes. It is an interesting fact that most of these capsuleforming bacteria only form these envelopes if growing either in the animal body or upon very special media,-fluid blood-serum, bronchial mucus, and also, according to Paulsen, upon milk.1 Upon gelatin, agar, and potato, nothing 1 Whether exquisite capsule-formation always occurs on these nutrient media, appears undecided. Recently, also, various authors have pointed out that capsule-like formations can be demonstrated in a wider field in the bacterial kingdom. Johne has described a method (see Technical Appendix) for anthrax by which the capsule can be Extensive of these capsules appears. See also, in the special part, Streptococcus involutus and mesenterioides. review of literature by Binaghi, C. B. L. IV, 919. Characteristic unilateral thickenings or swellings of the bacterial membrane are presented by Bact. pediculatum, which is described as an uncommon cause of the "frog-spawn disease" of sugar factories (Fig. 6). Regarding especially striking membrane thickening at the ends of threads (club formation), see those of actinomycetes. The outer surface of bacteria is often perfectly smooth and without appendages in the short bacilli, and almost always in the spherical forms, but the longer rods and spiral forms are usually provided with delicate single or multiple flagella. These are often distributed over the whole body of the bacterium, often form only a little bunch at one end, and often there is found but a single polar flagellum. Bacteria with polar flagella, shortly before division, show a Fig. 6.-Bact. pediculatum (after Koch and Hosäus). single flagellum or a bunch of flagella at each end. As A. Fischer particularly showed, flagella are not of the nature of retractile and extending pseudopodia, but true hair-like outgrowths. For the demonstration of flagella it is necessary to treat the bacteria with especially powerful staining agents. In this process the capsules of the bacteria, which remain unstained in the ordinary method, are stained, and so the bacteria appear very much thickened. Occasionally wide layers of capsule remain unstained and the flagella are then set upon a narrow ring-like halo, separated from the bacillus by a colorless zone (Zettnow, von Stöcklin, A. Fischer). Unfortunately, very many of the procedures made plainly visible; also in this manner distinct capsules are obtained in B. megatherium, oxalaticus, etc. Babes has depicted capsules in connection with the Streptococcus pyogenes, and we have ourselves occasionally seen similar formations in the case of many bacteria. Masses of bacteria which are united into mucous clumps by swelling of the capsules (often a sign of death) are called “zooglea.” |