Bacon, Sir Nicholas, father of Francis Bacon, Lord-Keeper of the Great Seal, born 1510, died 1579. Henry VIII gave him several lucrative offices, which he retained under Edward VI. He lived in retirement during the reign of Mary, but Queen Elizabeth appointed him Lord-Keeper for life. He was the intimate friend of Lord Burleigh, a sister of whose wife he married, and by her became the father of the great Chancellor.
Bacon, Roger, an English monk, and one of the most profound and original thinkers of his day, was born about 1214, near Ilchester,
Somersetshire, died at Oxford in 1294. He first entered the University of Oxford, and went afterwards to that of Paris, where he is said to have distinguished himself and received the degree of Doctor of Theology. About 1250 he returned to England, entered the order of Franciscans and fixed his abode at Oxford; but having incurred the suspicion of his ecclesiastical superiors, he was sent to Paris and kept in confinement for ten years, without writing-materials, books, or instruments. The cause seems to have been simple enough. He had been a diligent student of the chemical, physical, and mathematical sciences, and had made discoveries, and deduced results, which appeared so extraordinary to the ignorant that they were believed to be works of magic. This opinion was countenanced by the jealousy and hatred of the monks of his fraternity. In subsequent times he was popularly classed among those who had been in league with Satan. Having been set at liberty, he enjoyed a brief space of quiet while Clement IV was Pope; but in 1278 he was again thrown into prison, where he remained for at least ten years. Of the close of his life little is known. His most important work is his Opus Majus, where he discusses the relation of philosophy to religion, and then treats of language, metaphysics, optics, and experimental science. He was undoubtedly the earliest philosophical experimentalist in Britain; he made signal advances in optics; was an excellent chemist; and in all probability discovered gunpowder. He was intimately acquainted with geography and astronomy, as appears by his discovery of the errors of the calendar, and their causes, and by his proposals for correcting them, in which he approached very nearly to truth.—Cf. E. Charles, Roger Bacon, sa vie, ses ouvrages, ses doctrines.
1. Coccus. 2. Bacillus. 3. Spirillum (vibrio). 4. Spirillum (spirochæte).
Bacte´ria (Gr. baktērion, a rod), a general term applied to the lowest visible forms of life; other names given are germs or microbes. They are divided into three classes: (1) cocci—these are minute spheres about one twenty-five thousandth of an inch in diameter, arranged in chains or clusters; (2) bacilli—these are straight rods about the breadth of a coccus and two to four times as long; (3) spirilla—here there are two forms; one is like a bacillus, but curved (spirillum proper or vibrio); the other is a very fine spiral thread (spirochaete) often only half the thickness of a vibrio and two to six times as long. Bacteria consist of protoplasm surrounded by a membrane, and many show active movements; they all multiply asexually by splitting, and so rapidly may the process occur that 17,000,000 organisms or more may be formed from one bacterium in twenty-four hours. The chief part played by bacteria in nature is to cause putrefaction. They are found on all organic matter, and are therefore omnipresent. When grown artificially (see Bacteriology) they usually require organic matter for their food, and this they split up into simpler chemical compounds, some of which are very poisonous to animals (toxins); they can also split up sugars to produce various alcohols, acids, and gases. When certain of the bacilli are starved, the living matter gathers itself up into a spore surrounded by a very resisting membrane, and it can survive for a long time in this condition. All ordinary bacteria, including most of those which produce disease, can be killed by a few minutes' boiling, but the sporing varieties (e.g. many putrefactive forms) withstand much longer boiling—up to one and a half hours; they can also be killed by chemical means (see Disinfection). Many bacteria are useful to man, and a few give rise to disease (see Germ Theory).
All the above are magnified 560 times.
Bacteriology, the branch of science which deals with the structure and properties of bacteria. Though the existence of bacteria had been known from the time when Leeuwenhock arranged lenses so as to form a microscope, it was through the work of Pasteur that modern knowledge regarding the group originated. Pasteur's discovery that yeasts are the cause of the formation of alcohol from sugar was followed by his showing that bacteria are responsible for other processes of a similar character, e.g. the formation of vinegar from alcohol, the occurrence of the rancid change in butter, &c. When he went on to prove that a bacterium was the cause of a disease of silkworms, a stimulus was given to the germ theory of infection, and bacteriology was thus early brought intimately into contact with medical science. Another stimulus to bacteriological inquiry came from the controversy on spontaneous generation, and Pasteur was one of those who helped to establish the principle that the new development of living things, as represented by bacteria, out of non-living matter does not take place. This led to the inevitable deduction that all putrefactive processes are due to bacteria. On this Lister founded his antiseptic treatment of wounds, the practical effects of which focused attention on the important part played by bacteria in human affairs. The modern science of bacteriology really dates from 1877, when Koch proved that Bacillus anthracis is the cause of anthrax in
cattle. The outstanding feature of Koch's research was that in it, for the first time, methods were employed whereby all extraneous organisms were excluded from the inquiry, and the way was thus opened up for the study of the properties and effects of one species of bacterium acting by itself. The chief aspects of his work were as follows: (1) the determination of the temperatures at which bacteria are killed; the knowledge of this enables investigators to render free from living organisms their apparatus and the food materials (usually called media) necessary to support bacterial life (this is called sterilization); (2) the discovery that the insertion of a plug of cotton-wool in the neck of a vessel (e.g. a flask or test-tube) before its sterilization constitutes a sufficient filter, which prevents bacteria in the outside air gaining access to its interior or to any food medium placed in it for sterilization; (3) the elaboration of a series of media capable of acting as food for all the commonly occurring bacteria; (4) the introduction of a simple method of separating from one another bacterial species which in nature are often growing side by side. This is effected by making media containing a jelly (e.g. gelatine) which melts at a relatively low temperature. The bacterial mixture is well diluted in the melted medium, and this is poured out in a thin layer on a sterile glass plate and allowed to set. Each individual bacterial cell can thus multiply apart from neighbouring cells, and, it may be, in a few hours the resulting growth (a 'colony') is visible to the naked eye. A minute part of the colony is picked off with a heated needle and placed on a mass of sterile medium. In this way a 'pure culture' of each species present in the original mixture can be obtained. Koch's work was chiefly concerned with disease bacteria, and between 1880 and 1895 many such organisms were isolated in pure culture and their properties investigated (see Germ Theory of Disease).