Page:1902 Encyclopædia Britannica - Volume 26 - AUS-CHI.pdf/79

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BACKNANG — B ACTERIOLOGY 51 In 1901 the population was 2,291,812, showing an increase Back n ang1, a town of Wiirtemberg, Germany, 19 of 6 per cent. The land revenue and rates (1897-98) were miles by rail N.E. from Stuttgart, with an interesting Rs. 18,72,626 ; boys at school (1896-97) numbered 76,602, church (12th century), and notable tanneries and leather being 46’2 per cent, of the male population of school-going factories, also woollen and cloth mills. Population (1885), age; the registered death-rate (1897) was 42-46 per 1000. 6003; (1895), 7380. The number of police was 648. Backergunje is essentially a deltaic tract, traversed by numerous navigable water Back’s River {Thlewechodyeth, or Great Fish), a channels, which afford almost the only means of communi- river in Mackenzie and Keewatin districts, Canada, rising cation. By far the most important crop is rice, which is in Sussex lake, a small body of water in 108° 20' W. largely exported. Jute, oilseeds, betel-nuts, and coco-nuts long, and 64° 25' N. lat., and flowing north-eastward to are also grown. The only manufacture is pottery. The the Arctic Ocean, passing through several large lakeislands on the sea front are exposed to devastation by expansions—Pelly, Garry, and M‘Dougal—in its course. cyclonic storm-waves. On account of an epidemic of It was discovered and explored by Captain (afterwards Sir murders, disarmament has been enforced with good effect. George) Back in 1834. Its total length is 560 miles. BACTEfi 10 L 0 G Y. I. General. DURING the last decade of the 19th century enormous strides were made in the study of the ubiquitous and minute organisms known as Schizomycetes (bacteria). Schizo conviction that Cohn was right in remycetes. oarf^ng them as plants has gained ground, and is now generally accepted, but evidence has also accumulated to show that the group is a heterogeneous one, and that many forms usually included are not true Schizomycetes at all. That most of the typical bacteria have been derived from Cyanophyceas, such as Oscillaria, Xostoc, Arc., while Micrococcus, Sarcina, Arc., have their prototypes in Chroococcaceae, Palmellaceae, may be regarded as fairly well established, and forms like Beggiatoa and Spirochceta have their Algal analogues in Oscillaria and Spirulina ; but difficulties arise in several cases, especially since the flagella have become better known. Thaxter’s group of Myxobacteriaceae, if these turn out to be autonomous, points to alliances with the Myxomycetes, and the existence of ciliated Micrococci together with the formation of endospores—structures not known in the Cyanophyceae—reminds us of the flagellate Protozoa, e.g., Monas, Chromulina. Resemblances also exist between the endospores and the spore-formations in the Saccharomycetes, and if Bacillus inflalus, B. ventriculus, Arc., really form more than one spore in the cell, these analogies are strengthened. Schizomycetes such as Clostridium, Plectridium, Arc., where the sporiferous cells enlarge, bear out the same argument, and we must not forget that there are extremely minute “yeasts,” easily mistaken for Micrococci, and that yeasts occasionally form only one spore in the cell. Further, Schizo-saccharomyces is a genus of “ yeasts ” which combines the peculiarities of the two groups. Nor must we overlook the possibility that the endospore-formation in non-motile bacteria more than merely resembles the development of azygospores in the conjugatas, and some Ulothricacese, if reduced in size, would resemble them. Meyer regards them as chlamydospores, and Klebs as “ carpospores ” or possibly chlamydospores similar to the endospores of yeast. The former also looks on the ordinary disjointing bacterial cell as an oidium, and it must be admitted that since Brefeld’s discovery of the frequency of minute oidia and chlamydospores among the fungi, the probability that some so-called bacteria—and this applies especially to the branching forms accepted by some bacteriologists—are merely reduced fungi is increased. Even the curious one-sided growth of certain species which form sheaths and stalks—e.g., Bacterium vermiforme, B. pediculatum— can be matched by Algae such as Oocardium, Hydrums, and some Diatoms in this respect; and there are re-

semblances in other directions between Phragmidothrix and Bangia. That bacteria have existed from very early periods is clear from their presence in fossils; and although we cannot accept all the conclusions drawn from the imperfect records of the rocks, and may dis- Distribumiss as absurd the statements that geologically t,on' immured forms have been found still living, the researches

Fig. 1.—Preparations showing the various kinds of cilia and their arrangement. A, Bacillus subtilis Cohn, and Spirillum undula Ehrenb. ; B, Blatwcoccus citreus (Menge) Migula ; C, Pseudomonas pyocyanea (Gessard) Migula; D, P. macroselmis Migula ; E, J‘. syncyanea (Ehrenb.) Migula ; F, Bacillus typhi Gaflky; G, B. vulgaris (Hauser) Migula; H, Microspira Comma (Koch) Schroeter; J, K, Spirillum rubrum Esmarsch; L, M, S. undula (Muller) Ehrenb. (All after Migula.) of Renault and van Tieghem have shown pretty clearly that large numbers of bacteria existed in Carboniferous and Devonian times, and probably earlier. As regards their distribution in space, little is to be added. Several tropical species, especially the pathogenic forms—e.g., Vibrio cholerce, Am.—have been more thoroughly examined, but no geographical distribution of bacteria, in the sense used with