thread (where it is fixed) is wider and stronger. Also the height of the individual cells varies from one-half to four times the thickness, square forms being most common (Fig. 27, a and e).

Sometimes the terminal cell of a thread is large and oval (like a spore), in which case a deeper cell grows out laterally.

Propagation occurs through a peculiar breaking up of the cells at the end of a thread into fragments. Cohn distinguishes two types: (a) Formation of microgonidia: several individual cells in the thread break up by longitudinal and transverse division into not less than 16 very

Fig. 27.-Crenothrix polyspora. Cohn.

small plasma spheres, which later are freed from the somewhat swollen ends of the threads and grow out into new threads (Fig. 27, d). (b) Formation of macrogonidia: several of the cells in a thread near its end are transformed by infrequent division into larger, roundish, oval or diplococci-like forms, which grow out into new threads (Fig. 27, b). One type passes over into the other.

The plant is widely distributed (especially) in waters containing iron (also in tap-water). A pure culture in the bacteriologic sense has not been obtained. According to Rössler, cultivation readily succeeds in well-water in which pieces of brick are boiled and to which is added “some” ferrous sulphate. (Compare Ferd. Cohn, Beiträge zur

Biologie, Band 1, Heft 1, p. 108, Breslau; Rössler, Arch. f. Pharm., Bd. 233, 1895.)

Here also should be included the interesting Leptothrix ochracea Kützing, which does not belong to the leptothrices in a strict sense, because of its fully developed membrane. Winogradsky, who describes it in detail, gives the following characteristics: slender, jointed, fixed threads of bacilli, with membranes. The membrane is thick below, thin at the free ends, and the terminal rods are entirely without any membrane. The bacilli in the membrane are motile, but this motility is lost as soon as the membrane has reached a certain thickness. This variety thrives only in water containing ferrous oxid. In the metabolic process hydrated oxid of iron is deposited in the membrane. In hay decoction prepared from well-water and freshly precipitated hydroxid of iron the organism always grows easily and rapidly. It forms yellowish flakes and films, and in nature gives rise to extensive ocher deposits. (Compare Winogradsky, Bot. Zeitung, 1888, p. 261.)

Cladothrix dichotoma. Ferd. Cohn.

(Cohn's Beiträge, Bd. 1, Heft. III, p. 185.)

Long, apparently non-segmented threads, with thick or thin membranes, in part free, in part attached to putrefying algae. Thickness 1 to 5 μ. The pseudodichotomy is especially interesting. It is dependent upon the growing of a lower segment of a thread along by the side of a higher one (Fig. 30). Pure cultures of this organism have been but little studied; we have not possessed any. According to Büsgen, the most recent investigator of this organism (Ber. der deutsch. bot. Gesellschaft, 1894, p. 147), it grows slowly and without perceptible liquefaction in gelatin containing a little meat extract.

The surface growth consists of a "round white patch," which is not elevated, and from which, as from the stab, after a few days delicate threads grow out.

The threads have thin membranes when grown on gelatin and thick ones in dilute solutions of meat extract. The membrane is patent at the end of the threads, and through this opening, as also through irregularly occurring tears of

the membrane, there pass (by means of unilateral bunches of flagella, 8 to 12 μ long, according to G. Fischer, see Fig.

31), short, actively motile bacilli, which, after wandering, become fixed by one end and again form new threads.

There are no "spores

nor sporangia" unless the occasionally occurring expansions of the threads in which the rods lie in double rows are so called.

APPENDIX III.

Notes Concerning Insufficiently Elucidated Diseases Which Perhaps Depend upon Bacteria.

Of the diseases not yet mentioned in this book the following are outside of our consideration, because:

(a) Dependent upon higher molds: favus, herpes tonsurans, the deep wound suppurations caused by hyphomycetes, certain mold mycoses.

(b) Caused by yeast fungi: many tumors in man and animals.

(c) Dependent upon protozoa: malaria, dysentery (?), Texas fever in cattle, Surra or Tsetse disease, variola.

Some diseases which are probably produced by fissionfungi, as syphilis, are treated briefly in the text; some others are suited only to a discussion in an appendix, because that which is known regarding their etiology is either very uncertain or so incomplete that the insertion. of the micro-organisms in a system is not possible.

Phlyctenular (Scrofulous, Eczematous) Ophthalmitis.

In contrast to the authors who would recognize in the Micrococcus pyogenes alone the cause of the above-mentioned inflammations of the eye developing upon a scrofulous substratum, a number of investigators have shown. that in carefully selected uncomplicated cases, in a majority of the examinations, no micro-organisms were to be

found in the conjunctival phlyctenulæ and recent corneal infiltrations. See Axenfeld (C. B. xxiv, 194).

Beri-beri.

Regarding this important tropical disease, the literature. contains the most heterogeneous statements. The cause of the disease is recognized by Musso and Morelli (Compt. rend. de la Soc. de Biolog., 1893, 18) in an organism which is very closely related to the Micr. pyogenes a aureus; by Hunter, in agreement with Pekelharing and Winkler, in a white, motile staphylococcus (C. B. xxiv, 537).

Besides, there are those who conceive of beri-beri as a chronic intoxication (from sea animals), and place it in the same class with pellagra, etc. See Grimm (C. B. XXIV, 538).

Articular Rheumatism.

While some authors believe articular rheumatism is due to the Micrococcus pyogenes (see p. 184), Bannatyne, Wohlmann, and Blaxall (C. B. xx, 400) believe they have found its cause in a short, fine bacillus (2 μ long, 0.6

thick) which usually stains at the ends (eighteen positive cases!). In bouillon it slowly grows as small, fine puncta and crumbly particles. From the bouillon scanty growths upon agar and Löffler's serum may be obtained. According to the English writers, the organism is constantly found in the joint fluid; more rarely, and only in severe cases, in the blood. Leyden has found in five cases of endocarditis (C. B. XIX, 722) a fine diplococcus which can hardly be cultivated at all, and which may possibly be the cause of the disease.

Hospital Gangrene.

Vincent (A. P., 1896, 488) observed in Arabs, who were infected in Madagascar, in the typical cutaneous ulcers, very abundant, straight, rarely slightly bent, non-sporulating bacteria which do not stain by Gram's method. sections it is easily demonstrated in the characteristic loca

In