ordinary means. The beginner will often mistake involution forms for contaminations. Plate cultures soon determine whether one or more forms of bacteria are present. B. Chemical Composition of Bacteria. In Qualitatively considered, the bodies of bacteria1 consist in great part of water, salts, and albuminous bodies; 2 in lesser quantity are present extractive substances soluble in alcohol, and others soluble in ether (triolein, tripalmitin, tristearin, lecithin, cholestearin). In tubercle bacilli Aronson found in the ethereal extractive (25% of the dry substances), besides free fatty acids, large quantities of wax, whose alcohol differs from cholesterin. no variety of bacteria could E. Cramer find grape-sugar, although many varieties (Bacillus butyricus, varieties of leptothrix) contain starch-like masses, turning blue with iodin. True cellulose was found by Dreyfuss in B. subtilis and a bacillus resembling the B. coli; also, the Mycobacterium tuberculosis forms cellulose in the animal body. The vinegar-forming Bact. xylinum produces such a quantity that visiting cards have been made from it as a curiosity. From cultures of Myc. tuberculosis and a "capsule bacillus from water" resembling the B. pneumonia of Friedländer, on the contrary, no cellulose was obtained, but instead there was found abundant mucoid carbohydrates, CH1005, closely resembling hemicellulose. (For literature, see Nishimura, A. H. XVIII, 318, and XXI, 52). Scheibler (Chem. Centralbl. XI, 181) has described the mucus-like material of the Streptococcus mesenterioides as a 1H. Buchner has directed that the cell-contents (bacteria protoplasm) be obtained by trituration and the hydraulic press (3 to 500 atmospheres). Compare Hahn (C. B. XXIII, 86). Albumin and salts can constitute as much as 98% of the dry bodies of bacteria (Vibrio cholera); on the contrary, as much as 12% of carbohydrates may be present in the capsules. In bacterial albumin Hellmich recognized a globulin (Arch. f. exp. Pathol. u. Pharmak. XXVI, 345). Most improbable appears the statement of Fermi that he has grown nitrogen-free (!) micro-organisms (C. B. L. 11, 505). carbohydrate, CH1005, "dextran"; Kramer has obtained a similar substance from the capsules of the Bac. viscosus sacchari. Up to this time, nuclein has not been obtained from bacteria in any quantity; on the contrary, of the nuclein bases, xanthin, guanin, adenin have been obtained in considerable quantities. A number of bacteria contain sulphur granules, which have arisen from sulphuretted hydrogen (Beggiatoa thiothrix). Others, still considered as belonging to the bacteria by many authors, deposit oxid of iron in their capsules, obtaining it from water containing iron (cladothrix, crenothrix). Regarding quantitative composition, the methodical work of E. Cramer has added considerable light, though up to the present exact statements are submitted regarding only the B. prodigiosum, B. pneumoniæ, and some related organisms, and also a series of cultures of the Vibrio cholera. Compare E. Cramer, A. H. xIII, 71; xvi, 151, and xxii, p. 167. The water content of a culture grown on solid nutrient media, as also the amount of ash, depend in a very large measure upon the composition of the medium. For example, the B. prodigiosum contained, when grown upon potato, 21.49% dry substance, 2.70% ash in the fresh substance; when grown upon yellow turnip, 12.58% dry substance, 1.31% ash in the fresh substance. Besides the concentration of the nutrient medium, higher temperature and lessened age of the culture act to increase the dry substance and the ash. Also the dry substance of bacteria varies in its composition under the influence of the nutrient medium. Thus, for example, the Bact. pneumonia Fried. shows upon meatinfusion agar containing Evident increase in the proportion of peptone in the utrient medium leads to an increase in the albumin in the bacteria, while increase of grape-sugar makes the body substance poorer in albumin and increases the alcoholic and ethereal extractives (Lyons; A. H. xxvIII, 30). Yet there is much greater difference in the dry substance of the cholera vibriones, if they are grown at one time upon soda bouillon rich in albumin, and again upon Uschinsky's medium, free of albumin. Cramer here found as follows (the figures are the average from observations upon five cholera cultures): Cholera vibriones on soda-bouillon ALBUMIN ASH 31% Cholera vibriones on Uschinsky's solution. . 45 He found also in the latter case a considerable quantity of non-nitrogenous bodies, a part of which may be thought to be hydrocarbons (or fats). For the analysis of the ash of bacteria, consult Cramer (A. H. xxvIII) and de Schweinitz and Marion Dorset (C. B. XXIII, 993). The latter found almost only phosphate in the ash of tubercle bacilli. Of importance for the classification, even though more in a critically negative sense, is the fact, discovered by Cramer, that closely related varieties, which, upon many nutrient media, present analogous slightly varying composition, suddenly upon a new medium conduct themselves differently. Most interesting in this respect is the behavior of five cultures of cholera, which in soda bouillon furnished vibriones of almost exactly the same composition, but upon Uschinsky's1 solution presented very variable composition. SODA BOUILLON. USCHINSKY'S SOLUTION. Albumin. Ash. Total. Albumin. Ash. Total. Cholera, old This result shows again how dangerous it is to make a separation of two varieties because of any single chemical or biological reaction. In order to understand the astonishing differences, it is only necessary to recognize the ability of one of these varieties to form thick cell 1Compare p. 33. membranes from Uschinsky's solution. How easy it would be for an author to pronounce the cholera of Paris among this number, as a distinct species, since, upon Uschinsky's medium, it contains almost double the amount of albumin which the Hamburg cholera does. Bacterial spores have not so far, to my knowledge, been closely studied. One may naturally expect a decreased water-content, from the analogy to the spores of molds. C. Rapidity of Increase and Duration of the Life of Bacteria. Under favorable conditions (see below) bacteria multiply very rapidly; according to Buchner, the number of cholera vibriones, under most favorable conditions, is doubled in twenty minutes (C. B. II, 1). Compare also Ficker (C. B. xxi, 1059). The duration of the life of bacteria is theoretically unlimited, since from each cell by division two new ones, with unlimited possibilities of division, are produced. Practically, however, in our cultures the case is quite different. As pointed out by Gotschlich and Weigang, in a cholera culture (agar-streak) at 37°, even after twenty-four hours the number of live germs is practically reduced, and after forty-eight hours many bacteria are injured by their own products (Z. H. xx, 376). D. Conditions of Life of Bacteria. 1. NUTRIENT MEDIA. While a number of bacteria have hitherto been met with only in the human or animal organism as parasites, and appear to us as obligate parasites (example, Spirochæte Obermeieri), yet most of the parasites can be grown upon artificial nutrient media, either readily (example, Bacterium typhi) or with more difficulty (example, Micrococcus gonorrhea). Of the inhabitants of the inanimate surroundings of man, i. e., the so-called saprophytes, most are easily cultivated on artificial media, similar to those employed for parasites, while others-as, for example, saliva bacteria and certain water bacteria-offer great or in part insurmountable difficulties in their cultivation. All nutrient media for bacteria must be rich in water; the presence of salts, and sources for the supply of carbon and nitrogen are indispensable. Most varieties of practical importance and all pathogenic varieties prefer a medium containing albumin which is faintly alkaline in reaction. In some cases the demands of the bacteria as regards the composition of the nutrient medium are very different. As shown by Mead Bolton, a number of water bacteria (Bacillus aquatilis Flügge and B. erythrosporus Flügge) are contented with water which has been twice sterilized in glass vessels (Z. H. 1, 76). Here an increase of the bacteria must occur at the cost of traces of impurities, or of the ammonia and CO, of the atmosphere. Almost simultaneously Heraeus (Z. H. 1, 193) observed a variety of bacterium, which thrived in water which contained ammonium carbonate as the only source of carbon and nitrogen, being free from every organic nutrient material. Here, then, there occurred the elaboration of living substance from simple materials, just as occurs in the higher plants which work with chlorophyll aided by sunlight. Hüppe and Winogradsky have demonstrated by extensive studies the truth and importance of this observation. It appears that the energy necessary for the synthesis of albumin is obtained by oxidation of ammonia into nitric acid. Among the practically important bacteria, such unparticular ones are very few. Many allow albumin to be absent from the medium and are content with very simply composed nutrient solutions. Cultures upon such fluids were formerly much employed, and more recently Uschinsky has again experimented with simple nutrient solutions. The solution of Uschinsky is as follows: |