and of coagulating milk are gradually lost after long cultivation upon gelatin or agar.

Upon nutrient media free of sugar, there is a slight production of indol, but none of HS.

Distribution. Constantly cultivated from sour milk by Hüppe in Berlin, and by his pupils with slight modifications (consult Scholl). In Würzburg, since 1888 (compare Dissertation by Joh. Claus, Bakteriologische Untersuchung der Milch im Winter 1888-89 in Würzburg), we have never failed to find the organism in milk which had soured spontaneously and naturally, and until recently we had no doubt that it was the most important producer of lactic acid in milk, as Hüppe assumed. Milk which has soured spontaneously contains, in Würzburg, considerable quantities of volatile acid. As soon as possible the question as to the most important cause of lactic acid fermentation will be restudied in Würzburg. Compare page 224.

Demonstration and Differential Diagnosis. As differing from Bact. Güntheri, the Bact. acidi lactici grows well upon the ordinary nutrient media, and produces gas vigorously. As regards the staining by Gram's method, variations occur. In order to bring the findings into a scheme we call the forms not stained by Gram's method Bact. lactis aërogenes (see below), and leave the question open as regards the kind of relationship existing between these "species."

Bacterium aërogenes.1 (Kruse.) L. and N.

Synonyms. 2-Bacterium lactis aërogenes Escherich, Bacillus aërogenes Kruse.

Literature.-Escherich, Die Darmbakterien des Säuglings, 1886,

page 57.

1A Bact. lactis aërogenes obtained from Král presented from 1 to 3 irregularly arranged, long flagella, and was thus, according to our ideas, a typical Bact. coli. It also produced indol very vigorously.

2 We cannot understand how Kruse designates the Bact. acidi lactici as a variety of the Bact. aërogenes, which was described many years later. If one name is to be eliminated, according to priority, it must unquestionably be that of Bact. aërogenes.

This variety, first isolated from the milk-stools of infants by Escherich, is, according to our investigations, and according to Escherich's own statements, to be differentiated from the Bact. acidi lactici merely by the absence of staining by Gram's method 1-a characteristic upon which no great value can be placed according to recent experiences. A further difference, which Escherich understands from Hüppe's description, that Hüppe's organism was an obligate aerobe, we cannot recognize according to our investigations as present, for as often as we isolated the Bact. acidi lactici from sour milk in Würzburg, it always produced fermentation anaerobically. We cannot place any great value upon the luxuriant, sometimes hemispheric, slimy growth upon the surface in the gelatin stab, which he likens to the growth of the Bact. pneumoniæ. Escherich has even seen exceptions.

Metabolic Products.-Alcohol, acetic acid, active lactic acid, succinic acid, and, according to Nencki (C.-B. x, 82), also CO, and H. According to Smith, about 30%40% CO2, 60%-70% H. Indol is not produced.

For us Bact. lactis aërogenes is the name for a form without flagella, parallel to the typical peritrichous Bact. coli, or for a Bact. acidi lactici which is not stained by Gram's method. Transition forms certainly may exist,compare remark 1,—but one proved to be well founded is not certainly known to us. Very closely related is the Bact. diatrypeticum casei Baumann (C. B. xiv, 494), which is widely distributed in milk, water, and soil, and causes the cavities in cheese, or perhaps aids in their formation. Composition of gas: 63% CO2, 37% H2. It is provided with a capsule.

We can see no final proof in the investigations of Scheffer (A. H., 1897, xxx, 291) by which he attempts to make a distinction between the two varieties dependent upon immunization and agglutination experiments, for we remember that the different varieties of the streptococcus furnish no reciprocal immunity, and that each form of the Bact. coli furnishes a serum which strongly agglutinates only the form concerned.

1 Würtz and Lendet find both varieties identical.

Here belong the following non-motile varieties, which ferment grape- and milk-sugar:

Bacterium cavicida Brieger. Zeit. f. phys. Ch., 8.
Cultivated from a series of

Bacterium neapolitanum Emmerich.

cholera cadavers in Naples and once from the blood of a cholera patient. It is not the cause of cholera. According to Buchner, the moderate vibratory motion is not purely molecular. Flagella are not known. If it possessed flagella, then it would be considered as Bact. coli. Compare Weisser (Z. H. 1, 315).

Bacterium of septicemia of cats Lehm. and Neum. Cultivated from a cat which died spontaneously. Killed cats with typhoid symptoms. A more detailed description is still lacking.

Bacterium of dermatitis epidemica exfoliativa Russel (C. B. xv, 324). Unknown to us.

Bacterium caucasicum. (Kern.) L. and N.

Synonyms.-Dispora caucasica Kern. Bacillus caucasicus v. Freu

denreich.

Literature.-v. Freudenreich (C. B. L. III, 47, 87, 135).

Microscopic: Rods, about 5-6 μ long, 1 μ broad, which often present small, clear, globular swellings at the ends (are not spores!). Very slightly motile.

Fresh cultures grow poorly or not at all upon gelatin or milk-sugar gelatin; on the contrary, old cultures grow well. Upon milk-agar there develop whitish-gray, flat colonies with a somewhat jagged border due to outward projection of individual bacteria. Milk is not coagulated. Little gas-formation in milk; grows well in milk-sugar bouillon. Growth at 22° is feeble; 37° is the optimum.

V.

According to Kern, it is the cause of kephyr fermentation. Freudenreich obtained kephyr in sterile milk most often (not always) if he mixed together four varieties: (1) The kephyr yeast; (2 and 3) two streptococci isolated from kephyr; (4) the Bact. caucasicum; but also with the yeast and the two streptococci there resulted a tolerable production of kephyr.

Bacterium Güntheri. Lehm. and Neum.

and Thierfelder (A. H. xxv, 164).

Günther

Literature.-Günther and Thierfelder (A. H. xxv, 164). Leichmann (C. B. XVI, 826). Consult especially Leichmann (C. B. L. v, 344).

Nomenclature.-Günther and Thierfelder have not named their organism. In our first edition, published in May, 1896, we gave it the name Bacterium Güntheri L. and N. This name must stand, for also Leichmann, who had received the organism from Günther and Thierfelder,

but did not especially study it, designated it by the name Bacterium lactis acidi for the first time, so far as we can see, in December, 1896 (C. B. L. II, 777). Aside from the question of priority, it is very impractical to introduce a Bacterium lactis acidi, together with a Bacterium acidi lactici. Besides, Leichmann has also called a longer, slender, thermophilic, non-sporulating, acid-producing variety Bacillus lactis acidi. Later than our name is also Bacillus lacticus Kruse. Lately Kozai has introduced Bacillus acidi paralactici (Z. H. XXXI, 337).

Microscopic. Short rods, 1 long, 0.5-0.6μ thick, in pairs or short chains; at the ends somewhat pointed; stains by Gram's method; non-motile, facultative aerobe. Upon the gelatin plate: Punctiform colonies, never more than 0.5 mm. in diameter upon medium which does not contain sugar; when sugar is added, they are a little larger, but always very delicate, and never liquefying. In the stab culture there is often scarcely anything but a deep growth. Upon the agar plate: Delicate transparent growth, like the finest dewdrops. In bouillon: Slight cloudiness when no sugar is present, marked turbidity when sugar or milk are added. Milk Coagulated; reaction strongly acid. From grape- and milk-sugar pure dextrorotatory lactic acid (no other acid) is produced, but no gas. Upon potato there is a limited growth.

Distribution. According to Leichmann, Günther, Thierfelder, and Kozai, it is found in abundance in all spontaneously coagulated milk, and is either the general producer of lactic acid or, at least, the most important for certain places and times. Yet the single fact that spontaneously soured milk contains preponderantly the longknown inactive fermentation lactic acid, shows that other varieties besides the Bact. Güntheri are concerned in the process. Compare Leichmann (C. B. L. 11, 777).

Kozai (Z. H. XXXI, 337) has demonstrated for Halle that, especially at higher temperature, two varieties, which produce lactic acid, work together. They are given the names Bacillus acidi lævolactici and Micrococcus acidi paralactici liquefaciens Halensis. By this last name the necessity of the binomial nomenclature might be strikingly pointed out. Why not Micrococcus

halensis? The Bac. acidi lævolactici resembles, morphologically and biologically, the Bac. acidi lactici Hüppe, but at room temperature only coagulates milk slowly (often milk becomes a thick fluid only after twelve days), while in the incubator it coagulates milk rapidly. The acid formed is levorotatory lactic acid. The coccus is provided with a thick capsule, liquefies gelatin, and forms dextrorotatory lactic acid. During the final reading of our proof-sheets, Leichmann, in a partial work, claims to find in sour milk, besides his Bact. lactis acidi, also the Bact. acidi lactici-in the layer of cream, often even in preponderating number (C. B. L. v, 344).

Special Culture Methods.-Ordinary gelatin or agar plates do not give good results because of the minuteness of the colonies. The best medium to employ is a chalk medium (see Technical Appendix) which contains grapeor milk-sugar. Upon this the colonies are surrounded by a clear halo. Also good results are obtained with milkpeptone gelatin. One pays attention to the small colonies.

Bacterium pneumoniæ. Friedländer.1

(Plate 15.)

Literature.—Friedländer (Fortschr. d. Med., Bd. 1, 715, etc.).

Synonyms.-Pneumonia bacillus of Friedländer, capsule bacillus of pneumonia; also compare pages 227 and 228.

Microscopic Appearance.-Short rods (0.6-3.2 μ long, 0.5-0.8 μ broad), with rounded ends. When from the animal body, they present a thick gelatinous capsule, which is developed only in milk among the nutrient media.

Spontaneous motility is absent.

Staining Properties.-Stains by the usual methods

1 The Bact. tholaideum Gessner is only differentiated by its effect upon mice (A. H. IX, 129). Also the Bact. butyri colloideum Lafar (C. B. XIII, 807), constantly present in butter, according to Lafar, appears also related, although not yet sufficiently described biologically.