surroundings, and Bacon is not an exception. Those who take | After the fall of Napoleon he was given up to the Austrians, up such an extreme position regarding his merits have known too who allowed him to reside at Linz, on condition of never leaving little of the state of contemporary science, and have limited that town. He published a collection of poems at Pest, 1827 their comparison to the works of the scholastic theologians. (2nd ed. Buda, 1835), and also edited the poetical works of Anyos We never find in Bacon himself any consciousness of originality; and Faludi. He died at Linz on the 12th of May 1845. he is rather a keen and systematic thinker, working in a well- BACTERIOLOGY. The minute organisms which are combeaten track, from which his contemporaries were being drawn monly called "bacteria "I are also known popularly under other by theology and metaphysics.

designations, e.g. “microbes," "micro-organisms," “microBIBLIOGRAPHY.-The best work on Roger Bacon is perhaps that phytes," " bacilli," "micrococci.” All these terms, including of E. Charles, Roger Bacon, sa vie, ses ouvrages, ses doctrines d'après the usual one of bacteria, are unsatisfactory; for “ bacterium," and modern interpretation given in this work, are Schneider in his bacillus " and "micrococcus ” have narrow technical meanRoger Bacon, Eine Monographie (Augsburg, 1873); K. Werner, ings, and the other terms are too vague to be scientific. The Die Psychol. ...des Roger Bacon and Die Kosmologie ... des Roger most satisfactory designation is that proposed by Nägeli in 1857, Bacon (Vienna, 1879), S. A. Hirsch, Early English Hebraists (1899); namely "schizomycetes," and it is by this term that they are The new matter contained in the publications of Charles and Brewer usually known among botanists; the less exact term, however, is was summarized by H. Siebert, Roger Bacon: Inaugural Disserta- also used and is retained in this article since the science is comtion (Marburg, 1861). Cf. also J. K. Ingram, On the Opus Majus monly known as “ bacteriology.” The first part of this article åge" (reprinted from Journal des savans,

1848); E. Saisset

, pe deals with the general scientific aspects of the subject, while a curseurs et disciples de Descartes," pp. 1-58 (reprinted from Revue second part is concerned with the medical aspects. de deux mondes, 1861); K. Prantl, Gesch. der Logik, iii. 120-129 (a severe criticism of Bacon's logical doctrines); Held, Roger Bacon's

I. THE STUDY OF BACTERIA praktische Philosophie (Jena, 1881); Karl Pohl, Das Verhältniss d.

The general advances which have been made of late years Westminster Review, lxxxi. 1 and 512; A. Parrot, Roger Bacon e in the study of bacteria are clearly brought

to mind when we ses contemporains (1894); E. Fluegel, Roger Bacons Stellung in d. reflect that in the middle of the 19th century these organisms Gesch. d. Philos. (1902):'s. Vogl, Die Physik Roger Bacos (1906). were only known to a few experts and in a few forms as curiosities For the popular legend see Famous Historie of Fryer Bacon (London, of the microscope, chiefly interesting for their minuteness and Greene's Friar Bacon and Friar Bungay (1587 or 1588), and in motility. They were then known under the name of “animalBacon's Brazen Heade's Prophesie (1604). For Bacon as a classical organisms. At that time nothing was known of their life-history, publication of the Percy Society, vol. xv. 1844. A Piece of Friar culae," and were confounded with all kinds of other small scholar see J. E. Sandys, Hist. of Class. Schol: (2nd ed.,

1906), and no one dreamed of their being of importance to man and .

(R. AD.; X.) BACON (through the 0. Fr. bacon, Low Lat. baco, from a

other living beings, or of their capacity to produce the profound Teutonic word cognate with “ back,” e.g. O. H. Ger. pacho, M. H. chemical changes with which we are now so familiar. At the Ger. backe, buttock, flitch of bacon), the flesh of the sides and been described, but our knowledge of their biology has so ex

present day, however, not only have hundreds of forms or species back of the pig, cured by salting, drying, pickling and smoking. tended that

we have entire laboratories equipped for their study, BACONTHORPE [BACON, BACO, BACCONIUS), JOHN (d. 1346), and large libraries devoted solely to this subject. Furthermore, known as "the Resolute Doctor," a learned Carmelite monk, this branch of science has become so complex that the bacteriowas born at Baconthorpe in Norfolk. He seems to have been logical departments of medicine, of agriculture, of sewage, &c., the grandnephew of Roger Bacon (Brit. Mus. Add. MS. 19. 116). have become more or less separate studies. Brought up in the Carmelite monastery of Blakeney, near Walsingham, he studied at Oxford and Paris, where he was known devoid of chlorophyll and multiplying by repeated bipartitions.

The schizomycetes or bacteria are minute vegetable organisms as “ Princeps” of the Averroists. Renan, however, says that They consist of single cells, which may be spherical, he merely tried to justify Averroism against the charge of hetero-oblong or cylindrical in shape, or of filamentous or doxy. In 1329 he was chosen twelfth provincial of the English other aggregates of cells. They are characterized by the Carmelites. He appears to have anticipated Wycliffe in advocat-absence of ordinary sexual reproduction and by the absence ing the subordination of the clergy to the king. In 1333 he was of an ordinary nucleus. In the two last-mentioned

characters sent for to Rome, where, we are told, he first maintained the land in their manner of division the bacteria resemble Schizopope's authority in cases of divorce; but this opinion he retracted. He died in London in 1346. His chief work,

Doctoris resoluti phyceae (Cyanophyceae or blue-green algae), and the two groups Joannis Bacconis Anglici Carmelitae radiantissimi opus super class Schizophyta, to indicate the generally received view that

of Schizophyceae and Schizomycetes are usually united in the quattuor sententiarum libris (published 1510), has passed through most of the typical bacteria have been derived from the Cyanoseveral editions. Nearly three centuries later, it was still studied phyceae. Some forms, however, such as “Sarcina,” have their at Padua, the last home of Averroism, and Lucilio Vanini speaks algal analogues in Palmellaceae among the green algae, while of him with great veneration. See Brucker, Hist. Crit, iii . 865: Stöckl, Phil. d. Mittel, ii

. 1044 with the Myxomycetes. The existence of ciliated micrococci For information as to his life, not found otherwise and of doubtful together with the formation of endospores-structures not known accuracy, see J. B. de Lezana's Annales Sacri, iv.

in the Cyanophyceae-reminds us of the flagellate Protozoa, c.g. BACSANYI, JANOS (1763-1845), Hungarian poet, was born Monas, Chromuina. Resemblances also exist between the endoat Tapolcza on the inth of May 1763. In 1785 he published his spores and the spore-formations in the Saccharomycetes, and if first work, a patriotic poem, The Valour of the Magyars. In the Bacillus inflatus, B. ventriculus, &c., really form more than one same year he obtained a situation as clerk in the treasury at spore in the cell, these analogies are strengthened. Schizomycetes Kaschau, and there, in conjunction with other two Hungarian such as Clostridium, Plectridium, &c., where the sporiferous cells patriots, edited the Magyar Museum, which was suppressed by enlarge, bear out the same argument, and we must not forget that the government in 1792. In the following year he was deprived there are extremely minute" yeasts," easily mistaken for Microof his clerkship, and in 1794, having taken part in the conspiracy cocci, and that yeasts occasionally form only one spore in the cell. of Bishop Martinovich, he was thrown into the state prison of Nor must we overlook the possibility that the endosporethe Spielberg, near Brünn, where he remained for two years. formation in non-motile bacteria more than merely resembles After his release he took a considerable share in the Magyar the development of azygospores in the Conjugatae, and some Minerva, a literary review, and then proceeded to Vienna, where Ulothricaceae, if reduced in size, would resemble them. Meyer he obtained a post in the bank, and married. In 1809 he trans- regards them as chlamydospores, and Klebs as “carpospores” lated Napoleon's proclamation to the Magyars, and, in con- or possibly chlamydospores similar to the endospores of yeast. sequence of this anti-Austrian act, had to take refuge in Paris.

i Gr. Bartipov, Lat. bacillus, little rod or stick.

Definition.

Distribu tion In space.

The former also looks on the ordinary disjointing bacterial cell | liquid (blood, urine, milk, beer, &c.) containing organic matter, as an oidium, and it must be admitted that since Brefeld's dis- or any solid food-stuff (meat preserves, vegetables, &c.), allowed covery of the frequency of minute oidia and chlamydospores to stand exposed to the air soon swarms with bacteria, among the fungi, the probability that some so-called bacteria- if moisture is present and the temperature not aband this applies especially to the branching forms accepted by normal. Though they occur all the world over in the some bacteriologists-are merely reduced fungi is increased. air and on the surface of exposed bodies, it is not to be Even the curious one-sided growth of certain species which form supposed that they are by any means equally distributed, and sheaths and stalks-e.g. Bacterium vermiforme, B. pediculatum it is questionable whether the bacteria suspended in the air -can be matched by Algae such as Oocardium, Hydrurus, and ever exist in such enormous quantities as was once believed. some Diatoms. It is clear then that the bacteria are very possibly The evidence to hand shows that on heights and in open a heterogeneous group, and in the present state of our knowledge country, especially in the north, there may be few or even no their phylogeny must be considered as very doubtful. Schizomycetes detected in the air, and even in towns their Nearly all bacteria, owing to the absence of chlorophyll, are distribution varies greatly; sometimes they appear to exist in saprophytic or parasitic forms. Most of them are colourless, but minute clouds, as it were, with interspaces devoid of any, but in laboratories and closed spaces where their cultivation has been promoted the air may be considerably laden with them Of course the distribution of bodies so light and small is easily influenced by movements, rain, wind, changes of temperature, &c. As parasites, certain Schizomycetes inhabit and prey upon the organs of man and animals in varying degrees, and the conditions for their growth and distribution are then very complex. Plants appear to be less subject to their attacks-possibly, as has been suggested, because the acid fluids of the higher vegetable organisms are less suited for the development of Schizomycetes; nevertheless some are known to be parasitic on plants. Schizomycetes exist in every part of the alimentary canal of animals, except, perhaps, where acid secretions prevail; these are by no means necessarily harmful, though, by destroying the teeth for instance, certain forms may incidentally be the forerunners of damage which they do not directly cause.

紅線

History.

Little was known about these extremely minute organisms before 1860. A. van Leeuwenhoek figured bacteria as far back as the 17th century, and O. F. Müller knew several important forms in 1773, while Ehrenberg in 1830 had advanced to the commencement of a scientific separation and grouping of them, and in 1838 had proposed at least sixteen species, distributing them into four genera. Our modern more accurate though still fragmentary knowledge of the forms of Schizomycetes, however, dates from F. J. Cohn's brilliant researches, the chief results of which were published at various periods between 1853 and 1872; Cohn's classification of the bacteria, published in 1872 and extended in 1875, has in fact dominated the study of these organisms almost ever since. He proceeded in the main on the assumption that the forms of bacteria as met with and described by him are practically constant, at any rate within limits which are not wide: observ

FIG. 1. Preparations showing various forms of bacteria and the ing that a minute spherical micrococcus or a rod-like bacillus various types of cilia and their arrangement.

A. Bacillus subtilis, Cohn, and
Spirillum undula, Ehrenb.
B. Planococcus citreus (Menge),
Migula. [sard), Migula.
C. Pseudomonas pyocyanea (Ges
D. P. macroscimis, Migula.
E. P. syncyanea (Ehrenb.),
Migula.

F. Bacillus typhi, Gaffky.

G. B. vulgaris (Hauser), Migula.
H. Microspira Comma (Koch),
J, K. Spirillum rubrum, Es-

Schroeter.

marsch.

L,M.S. undula (Müller), Ehrenb.
(All after Migula.)

a few secrete colouring matters other than chlorophyll. In size their cells are commonly about 0·001 mm. (1 micromillimetre or I μ) in diameter, and from two to five times that length, but smaller ones and a few larger ones are known. Some of the shapes assumed by the cells are shown in fig. 1.

Distribu tion la time.

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 dismiss as absurd the statements that geologically immured forms have been found still living, the researches of Renault and van Tieghem have shown pretty clearly that large numbers of bacteria existed in Carboniferous and Devonian times, and probably earlier.

Schizomycetes are ubiquitous as saprophytes in still ponds and ditches, in running streams and rivers, and in the sea, and especially in drains, bogs, refuse heaps, and in the soil, and wherever organic infusions are allowed to stand for a short time. Any

regularly produced similar micrococci and bacilli respectively, he based his classification on what may be considered the constancy of forms which he called species and genera. As to the constancy of form, however, Cohn maintained certain reservations which have been ignored by some of his followers. The fact that Schizomycetes produce spores appears to have been discovered by Cohn in 1857, though it was expressed dubiously in 1872; these spores had no doubt been observed previously. In 1876, however, Cohn had seen the spores germinate, and Koch, Brefeld, Pratzmowski, van Tieghem, de Bary and others confirmed the discovery in various species.

The supposed constancy of forms in Cohn's species and genera received a shock when Lankester in 1873 pointed out that his Bacterium rubescens (since named Beggiatoa roseo-persicina, Zopf) passes through conditions which would have been described by most observers influenced by the current doctrine as so many separate species or even genera,"-that in fact forms known as Bacterium, Micrococcus, Bacillus, Leptothrix, &c., occur as phases in one life-history. Lister put forth similar ideas about the same time; and Billroth came forward in 1874 with the extravagant view that the various bacteria are only different states of one and the same organism which he called Cocco-bacteria septica. From that time the question of the pleomorphism (mutability of shape) of the bacteria has been hotly discussed; but it is now generally agreed that, while a

certain number of forms may show different types of cell during reproducing itself had been entertained. Such vague notions the various phases of the life-history,' yet the majority of forms began to take more definite shape as the ferment theory of are uniform, showing one type of cell throughout their life-Cagniard de la Tour (1828), Schwann (1837) and Pasteur made history. The question of species in the bacteria is essentially way, especially in the hands of the last-named savant From the same as in other groups of plants; before a form can be about 1870 onwards the " germ theory of discase” has passed placed in a satisfactory classificatory position its whole life into acceptance. P. F. 0. Rayer in 1850 and Davaine had history must be studied, so that all the phases may be known. observed the bacilli in the blood of animals dead of anthrax In the meantime, while various observers were building up our(splenic fever), and Pollender discovered them ancw in 1855 knowledge of the morphology of bacteria, others were laying the In 1863, imbued with ideas derived from Pasteur's rescarches foundation of what is known of the relations of these organisms on fermentation, Davaine reinvestigated the matter, and put to fermentation and disease-that ancient will-o'-the-wisp forth the opinion that the anthrax bacilli caused the splenic

spontaneous generation " being revived by the way. When fever; this was proved to result from inoculation. Koch in Pasteur in 1857 showed that the lactic fermentation depends 1876 published his observations on Davaine's bacilli, placed on the presence of an organism, it was already known from beyond doubt their causal relation to splenic fever, discovered the researches of Schwann (1837) and Helmholtz (1843) that the spores and the saprophytic phase in the life-history of the fermentation and putrefaction are intimately connected with organism, and cleared up important points in the whole question the presence of organisms derived from the air, and that the (figs. 7 and 9). In 1870 Pasteur had proved that a disease of preservation of putrescible substances depends on this principle. silkworms was due to an organism of the nature of a bacterium; În 1862 Pasteur placed it beyond reasonable doubt that the and in 1871 Oertel showed that a Micrococcus already known to ammoniacal fermentation of urea is due to the action of a minute exist in diphtheria is intimately concerned in producing that Schizomycete; in 1864 this was confirmed by van Tieghem, disease. In 1872, therefore, Cohn was already justified in and in 1874 by Cohn, who named the organism Micrococcus grouping together a number of " pathogenous” Schizomycetes. ureae. Pasteur and Cohn also pointed out that putrefaction is Thus arose the foundations of the modern "germ theory of but a special case of fermentation, and before 1872 the doctrines disease;" and, in the midst of the wildest conjectures and the of Pasteur were established with respect to Schizomycetes.worst of logic, a nucleus of facts was won, which has since Meanwhile two branches of inquiry had arisen, so to speak, grown, and is growing daily. Septicaemia, tuberculosis, glanders, from the above. In the first place, the ancient question of fowl-cholera, relapsing fever, and other diseases are now brought

spontaneous generation " received fresh impetus from the definitely within the range of biology, and it is clear that difficulty of keeping such minute organisms as bacteria from all contagious and infectious diseases are due to the action reaching and developing in organic infusions; and, secondly, of bacteria or, in a few cases, to fungi, or to protozoa or other the long-suspected analogies between the phenomena of fer- animals. mentation and those of certain diseases again made themselves Other questions of the highest importance have arisen from felt, as both became better understood. Needham in 1745 had the foregoing. About 1880 Pasteur first showed that Bacillus declared that heated infusions of organic matter were not anthracis cultivated in chicken broth, with plenty of oxygen deprived of living beings; Spallanzani (1777) had replied that and at a temperature of 42-43° C., lost its virulence after a few more careful heating and other precautions prevent the appear-generations," and ceased to kill even the mouse; Toussaint ance of organisms in the fluid. Various experiments by Schwann, and Chauveau confirmed, and others have extended the observaHelmholtz, Schultz, Schroeder, Dusch and others led to the tions. More remarkable still, animals inoculated with such refutation, step by step, of the belief that the more minute attenuated ” bacilli proved to be curiously resistant to the organisms, and particularly bacteria, arose de novo in the special deadly effects of subsequent inoculations of the non-attenuated cases quoted. Nevertheless, instances were adduced where the form. In other words, animals vaccinated with the cultivated most careful heating of yolk of egg, milk, hay-infusions, &c., bacillus showed immunity from disease when reinoculated with had failed, -the boiled infusions, &c., turning putrid and the deadly wild form. The questions as to the causes and swarming with bacteria after a few hours.

nature of the changes in the bacillus and in the host, as to the In 1862 Pasteur repeated and extended such experiments, extent of immunity enjoyed by the latter, &c., are of the greatest and paved the way for a complete explanation of the anomalies; interest and importance. These matters, however, and others Cohn in 1872 published confirmatory results; and it became such as phagocytosis (first described by Metchnikoff in 1884), clear that no putrefaction can take place without bacteria or and the epoch-making discovery of the opsonins of the blood by some other living organism. In the hands of Brefeld, Burdon-Wright, do not here concern us (see II. below). Sanderson, de Bary, Tyndall, Roberts, Lister and others, the MORPHOLOGY.-Sizes, Forms, Structure, &c.—The Schizomyvarious links in the chain of evidence grew stronger and stronger, cetes consist of single cells, or of filamentous or other groups of and every case adduced as one of "spontaneous generation" cells, according as the divisions are completed at once fell to the ground when examined. No case of so-called "spon- or not. While some unicellular forms are less than taneous generation " has withstood rigid investigation; but the 1% (091 mm.) in diameter, others have cells measurdiscussion contributed to more exact ideas as to the ubiquity, ing 4u or su or even 7 or 8 in thickness, while the length may minuteness, and high powers of resistance to physical agents vary from that of the diameter to many times that measurement. of the spores of Schizomycetes, and led to more exact

ideas In the filamentous forms the individual cells are often difficult of antiseptic treatments. Methods were also improved, and to observe until reagents are applied (e.g. fig. 14), and the length the application of some of them to surgery at the hands of of the rows of cylindrical cells may be many hundred times Lister, Koch and others has yielded results of the highest greater than the breadth. Similarly, the diameters of flat or value.

spheroidal colonies may vary from a few times to many hundred Long before any clear ideas as to the relations of Schizomycetes times that of the individual cells, the divisions of which have to fermentation and disease were possible, various thinkers at produced the colony. The shape of the individual Cell-wall. different times had suggested that resemblances existed between cell (fig. 1) varies from that of a minute sphere to the phenomena of certain diseases and those of fermentation, that of a straight, curved, or twisted filament or cylinder, and the idea that a virus or contagium might be something of which is not necessarily of the same diameter throughout, and the nature of a minute organism capable of spreading and may have flattened, rounded, or even pointed ends. The rule is

that the cells divide in one direction only-i.e. transverse to the Cladothrix dicholoma, for example, which is ordinarily a branched. long axis and therefore produce aggregates of long cylindrical number of separate cells which develop a tuft of cilia and escape

from shape; but in rarer cases iso-diametric cells divide in two or the sheath. Such a behaviour is very similar to the production of three directions, producing flat, or spheroidal, or irregular 200spores which is so common in many filamentous algae. colonies, the size of which is practically unlimited. The bacterial

Form and structure.

Cell-wall

a

Дат

3.30

A

830

2pm

40

630 B

20

12 pm

12pm.

b

2pm 40

a

1.am

cell is always clothed by a definite cell-membrane, as was shown | accordingly been directed to the deeply-staining granules by the plasmolysing experiments of Fischer and others. Unlike mentioned above, and the term chromatin-granules has been the cell-wall of the higher plants, it gives usually no applied to them, and they have been considered to represent reactions of cellulose, nor is chitin present as in the a rudimentary nucleus. That these granules consist of a material fungi, but it consists of a proteid substance and is apparently similar to the chromatin of the nucleus of higher forms is very a modification of the general protoplasm. In some cases, how- doubtful, and the comparison with the nucleus of more highly ever, as in B. tuberculosis, analysis of the cell shows a large organized cells rests on a very slender basis. The most recent amount of cellulose. The cell-walls in some forms swell up into works (Vejdovsky, Mencl), however, appear to show that nuclei a gelatinous mass so that the cell appears to be surrounded in of a structure and mode of division almost typical are to be found the unstained condition by a clear, transparent space. When in some of the largest bacteria. It is possible that a similar the swollen wall is dense and regular in appearance the term structure has been "capsule" is applied to the sheath as in Leuconostoc. Secreted overlooked or is inpigments (red, yellow, green and blue) are sometimes deposited visible in other in the wall, and some of the iron-bacteria have deposits of oxide forms owing to of iron in the membranes. their small size, and that there may be another type of nucleus-the diffuse nucleus - such as Schaudinn believed to be the case in B. butschlii. Many bacteria when suspended in a fluid exhibit a power of independent movement which is, of course, quite distinct from the Brownian movement-a non-vital phenomenon common to all finelydivided particles suspended in a fluid. Independent movement is effected by special motile organs, the cilia or flagella. These H visible, with ordinary illumination in living cells or unstained preparations, and can only A. made clearly visible by special methods of preparation and staining B. first used by Löffler. By these methods the cilia are seen to be fine protoplasmic C. outgrowths of the D, cell (fig. 1) of the, F. same nature as those of the zoospores and G. antherozoids of algae, mosses, &c. These cilia appear to be attached to the cell-wall, being unaffected by plasmolysis, but Fischer states that they really are derived from the central protoplasm and pass through minute pores in the wall. The cilia may be present during a short period only in the life of a Schizomycete, and their number may vary according to the medium on which the organism is growing. Nevertheless, there is more or less constancy in the type of distribution, &c., of the cilia for each species when growing at its best. The chief results may be summed up as follows: some species, e.g. B. anthracis, have no cilia; others have only one flagellum at one pole (Monotrichous), e.g. Bacillus pyocyaneus (fig. 1, C, D), or one at each pole; others again have a tuft of several cilia

such segments.

A. The spore sown at 11 A.M., as shown at a, had swollen (b) perceptibly by noon, and had germinated by 3.30 P.M., as shown at c:ind at 6 P.M., and e at 8.30 P.M.; the resulting filament is segmenting into bacilli as it elongates, and at midnight () consisted of twelve B, C. Similar series of phases in the order of the small letters in each case, and with the times of observation attached. At f and g occurs the breaking up of the filament into rodlets. D. Germinating spores in various stages, more highly magnified, and showing the different ways of escape of the filament from the spore-membrane. (H. M. W.)

structures are in

be

FIG. 3.-Types of Zoogloea. (After Zopf.)
Mixed zoogloea found as a pellicle on the
surface of vegetable infusions, &c.; it
consists of various forms, and contains
cocci (a) and rodlets, in series (b and c),
&c.
Egg-shaped mass of zoogloea of Beggiatoa
roseo-persicina (Bacterium rubescens of
Lankester); the gelatinous swollen walls
of the large crowded cocci are fused into
a common gelatinous envelope.
Reticulate zoogloea of the same.
E, H. Colonies of Myconostoc enveloped
Branched fruticose zoog foea of Cladothrix
(slightly magnified).
Zoogloea of Bacterium merismopedioides,
Zopf, containing cocci arranged in tablets.