Ritchie has recently shown that tetanus toxine if mixed with a proportion of acid does not give rise to tetanic symptoms when injected into a susceptible animal, but a degree of immunity is nevertheless produced. It is quite possible therefore that some inactivation of the toxine produced occurs, and that a certain amount of immunity is produced thereby, but that under increased dose the immunity breaks down. 181 CHAPTER XII. Bacteria only met with in the Mouth. A NUMBER of bacteria occur with great regularity in all unclean mouths, and wherever any deposit of calculus exists. They exhibit the peculiarity that they will not grow upon ordinary culture media, at any rate when material containing them is inoculated directly from the mouth; they may appear in the abscesses and local inflammations produced in animals, by the inoculation of material taken from the gum margins. Miller was the first to attempt a classification of these mouth organisms, his tabulation being as follows: (1) Leptothrix innominata. (2) Leptothrix buccalis maxima. (3) Bacillus buccalis maximus. (6) Iodo coccus vaginatus. Miller found that all these organisms refused to grow upon the ordinary culture media, and in no case was he able to obtain a pure cultivation; occasionally some of the bacteria grew a little, but they soon died out. This question of cultivation is one of the chief difficulties in isolating the above organisms, as not only do they require special media, but they are particularly susceptible to the presence of other bacteria; the mouth streptococcus, in particular, growing down almost all other forms. It is probable that the morphological forms tabulated above will ultimately prove to be related to more than the six species they now represent, but until they have all been obtained in pure culture Miller's tabulation should stand. I have succeeded in cultivating two at least of the organisms in the above list, and it is to be hoped that the others may ultimately be obtained in pure culture. Two other organisms may be added to Miller's list, one the Leptothrix racemosa of Vicentini, and the Streptothrix buccalis described by myself. The Group Leptothrix.-A great deal has been written concerning "Leptothrix," and all sorts of curious things said of the doings of the mythical "Leptothrix of tooth decay." Any threadforming organism has been included under the term, so that not a little confusion exists in the nomenclature; more particularly has this arisen from the fact that no definite rule has been followed, and no proper definition of Leptothrix adhered to. FIG. 56.-SHOWING VARIOUS FORMS FROM THE MOUTH DIRECT. The fine threads are Miller's Leptothrix innominate, the thick chain of bacilli B. maximus buccalis. The term Leptothrix signifies a genus of bacteria belonging to the higher forms of Schizomycetes, and nearly related to the Crenothrix and Beggiatoia. Zoph, in his classification of bacteria, describes the genus Leptothrix as "spherical, rod-shaped, and filamentous forms, the last showing a difference between the two extremities; spore formation not known, filaments straight or spiral." Migula has proposed as a family name for the various higher bacteria, Chlamydobacteriacea, and defines them as "filamentous bacteria composed of rod-shaped Division of the cells cells and surrounded with a distinct sheath. The divisions of Migula's Chlamydobacteriaceæ are:- A.-Filaments unbranched. (i.) Cell division in one direction of space only (a) (Leptothrix). (ii.) Cell division before gonidia formation in three directions of space. (a) Filaments with scarcely discernible sheath (Phragmidiothrix). (b) Filaments with easily discernible sheath B. Filaments show false branching (Cladothrix). Zoph includes Crenothrix, Phragmidothrix, Leptothrix and Beggiatoa under the one family Leptotricheæ. Lehmann and Neumann class Leptothrix, Cladothrix dichotoma (F. Cohn), Beggiatoa, Phragmidothrix and Crenothrix under the term Higher fusion algæ, but disclaim personal knowledge of the group. Several species of Cladothrix and Streptothrix are merged in the genus Actinomyces. From the above brief review of the literature it will be seen that considerable diversity of opinion exists as to the proper grouping of these higher bacteria; Migula's classification appears to be the one to which least objection can be taken, and is moreover capable of extension, if necessary, to include new forms. Whatever be the exact definition of Leptothrix decided upon, it is clear that bacilli which are able at times to form threads cannot on that account alone be included as Leptotriches; it is, however, impossible to state whether the curious bacillary forms often met with in the mouth are members of the above family or merely involution forms of other bacteria. I am inclined to think that a number of the morphological forms often seen are related to the Blastomycetes, more particularly as cultivations containing these forms often result in the growth of certain yeasts, many of which produce distinct filamentous forms on some media, but I am unable at present to make any definite statement as to the relationship. The yeast filaments often give the granulose reaction. One organism that is known as Leptothrix epidermidis,1 produces coiled up and twisted filaments which are slightly motile but show no flagella; the movement is thought to be due to contractility of the organism itself. This organism is said to be common on the skin of man. It is quite impossible to discuss all the isolated species individually termed "Leptothrix" until fuller knowledge of their biology has been obtained; the species described by various authors are therefore given without any attempt at arrangement, but it is to be hoped that further work will contribute largely to our knowledge of the subject. The organism described by Vignal as Leptothrix buccalis is supposed to be identical with Leptothrix buccalis of Robin. The organism described by Vignal is a large bacillus, and is the same I have described as B. maximus as far as it is possible to judge from Vignal's observations. The organism does not merit the term Leptothrix, and Miller's term B. maximus is retained (see below). Leptothrix Placoides alba (Dobrzyniecki, Cent. für. Bakt., B. xxi., 225), obtained only once, from a root filling removed after four years. Morphology. Chains of bacilli forming tangled skeins (not branching?); on staining, bacillary and cocci-like bodies are seen in the centre of the threads. The threads are not motile. Staining Reactions.-Stains by Gram's method, and with the ordinary aniline dyes, best with aniline-gentian violet or fuchsin. Stains blue with acidulated Gram's iodine (granulose reaction). Biological Characters. An äerobic, liquefying, non- motile bacillus. Spore formation not observed. Gelatin Plates.—In forty-eight hours round minute raised white colonies composed of masses of threads resembling the colonies of B. anthracis. In three days the gelatin around the colonies becomes liquefied and the colony floats in the fluid. Gelatin Streak.-Development slow, in four to five days minute white colonies appear, liquefaction commencing about the tenth day. 1 Byzozero. Cent. für. Bakt., xx., p. 606., Nos. 16-17. |