BACTERIA, organisms that comprise a class of low plants, the importance of which is due to their power of producing profound changes in life. The terms bacteria, germs, microbes, bacilli, are popularly used to denote these micro scopic objects. Bacillus means a little rod. The term is properly applicable to only such microbes as are rod-shaped. The word microbe (from the Greek, Inikros, small, and bios, life) is a term which was coined to include all of the microscopic plants commonly included under the terms bacteria and yeasts.
Plants or Anima/s.—Bacteria possess characteristics of plants and animals. They resemble animals in their common power, independent motion, and in their habit of living upon complex bodies for food. But in general form, methods of growth, and formation of threads and spores they resemble plants. Though there are hundreds of different species there are only three general forms— spheres, rods, and spirals, reminding of billiard balls, pencils, and corkscrews. There is sonic, though slight, variation in size. All are extermely minute and never visible to the naked eye. They range in size from 1-100000th to 1-3000th of an inch. Some species have the power of active motion, and may be seen moving rapidly to and fro in the liquid in which they are growing. This motion is produced by flagella, which protrude from the body.
Marvelous Multiplication.—They mul tiply by simple division or fission. Each individual elongates and then divides in the middle into similar halves; each of which then repeats the process. With some species the individuals remain attached after division, forming long chains; others produce solid groups of fours, eights, or sixteens. Some species that have been carefully watched under the microscope have been found, under favorable conditions, to grow so rapidly as to divide every half hour. At this rate in one day each microbe would produce over 16.000,000 descend ants. At the end of the third day they would number millions of millions, the bulk and weight of which would be enormous. were it not that their rate of multiplication is checked either by lack of food or by the accumulation of their own excreted products, which are injurious to them.
Harmful Bacteria. — Bacteria abound in all putrescent or fermenting mixtures containing organic matter, and are the cause of fermentation and putrefaction. Some are present in, and the cause of, certain of the zymotic or ferment diseases, such as malignant pustule, erysipelas, tuberculosis, etc. Micrococci are spheroidal bacteria, and very small, never more than 1-23000th of an inch in diameter, often less. If they are kept out of surgical wounds, there is no sup puration. The discovery of this fact made hundreds of operations possible which of old were thought to be out of the reach of art—hence the wonderful success of antiseptic surgery.
Bacillus Tuberculosis. — Very great interest-attaches to the bacillus tuber culosis, which is so constantly present that it is used as a means of differen tiating the inflammatory diseases of the lungs from tuberculosis. This organism always produces the disease when inoculated into animals. Statistics have been published showing that the bacillus was present in 2,417 out of 2,509 cases of supposed tuberculosis.
Useful Bacteria,—In many respects bacteria are man's greatest benefactors; for upon their activities is founded the continued life of the animal and vege table kingdoms. As microbes consume the material which serves them as food they produce chemical changes therein, resulting in simpler products called decomposition or cleavage products. Sometimes, however, they possess the power of building other compounds out of fragments, thus building up as well as tearing down. There are various industries based upon the decomposition powers of bacteria—viz., the maceration industries—in the separation of the valuable fibers from the useless fibrous material in the preparation of linen, jute, hemp, and cocoanut fiber; also in the commercial preparation of sponges, and often in the early stages of leather preparation. Some 50 years ago it was found that the mysterious substance known to brewers as yeast or barm was really composed of a vast number of minute oval particles that are endowed with the powers of growth and multi plication, and, therefore, undoubtedly living.