Bacteria

the name applied to certain organisms microscopic size, which constitute the lowest of those forms of vegetable life called The divisions of the group of fungi have many changes of nomenclature of late it is now customary to apply the term 320 “ bacteria” botanists fact Figs. a ume spherical of shaped shaped a and are as thus, cidentally this tunately double several here ing as forms, of spoken to cocci.” occur, stance, ganism Koch's lus, such are and. as long wound * Bacteria. Seen ETAT as a synonym as the Schizomycetes that bacteria multiply 1 and 2,—TURERCLE (From a polog an by Bousfleli, Esq. various shapes forms known these may adhere together double coccus forms are little staff); intermediate bacilli, Ze. short still spoken of, “bacteria”; and as already in observed, word is unforused in a sense. Again rods may adtogether form filaments known “ Leptothrix ” while chains micrococci are of as “strep- | Curved rods also as, for in in the or known as cholera baciland if several curved bacilli united, end to the pesulting spirillum, while a and closely spiral is called Some bacteria are flagellum,” which gives seme for BACILLUS. E. C. (see as or called rods, Fig. yg. —sraterococcb st a splrochsta. provided them the division or fi ion by repeated justifies cation derived from words sulit, Sungus. bacterium little at served members group mycetes, already whole commonly of as bacteria cells; their obtained study noting fying ployed. Plate). “micrococci;” forming “ diplococcus;” “bacilli” forms used to 8,—DIPHTHERIA octela, with the ( 292 known to fang i. The division the appliof this term, as it is two Greek oxl{w, to and puxns, @ The word means a rod, and was one time ref or certain of the of Schizo but as stated the group is now spoken bacteria. The are single an idea of size may be from a of the plate. the magnipower em- They may There are two a dumb-bell rod- (bacillus, between cocci be called, and (KLEES rvooenen Kort B.C. a whip-like power of ‘active ) movement, lations humble weeds. unicellular, many difference, green absence obtaining must pounds, other upon attacking liarity study and of tions, gave these be working was by that it into vinegar the the whether also great hand, material there, other was to in preserved was units tion; place water however, was and to wool undetgoing plug change and reaching Nutrient from their bacterial the without. ployed Bacteria. others are non-motile. Very near reof the bacteria are met with in certain members of the great family of alge or sea- ‘These lowliest alge are, like the bacteria, devoid of sexual organs, and present other points of similarity, but one great namely, that they contain the peculiar cone matter known as chlorophyll. The of chlorophyll in bacteria prevents their carbon from carbonic acid gas, and they therefore live upon ready-formed carbon com such as exist in animals or plants. In words, the bacteria are parasitic, feeding organic matter, and in some cases actually living organisms. It is this last pecuwhich attaches such vast importance to the of bacteria, and the researches of Pasteur others, which have shown how the life history fi ion fungi is bound up with certain ferment a with putrefaction, and finally with disease, a powerful impetus to the scientific study of minute plants, which are now recognised to fraught with the most wonderful power for good or ill to higher forms of life. The importance of the study of bacteria, then, first recognised in investigating the réle played them in fermentation proce es. Pasteur showed muk turns sour because of the growth within of a bacterium, which converts the sugar of milk lactic acid; again, in the manufacture of a bacterium is at work, and is the cause of conversion of alcohol into acetio acid. After establishment of these facts the question arose the phenomena of putrefaction might not be due to bacterial growth, and this led to a controversy. It was maintained, on the one that bacteria could never develop in nutrient unle similar bacteria already existed or were introduced from without; on the hand, the doctrine of spontaneous generation upheld, and it was urged that it was impo ible prevent putrefactive proce es from occurring organic infusions, however carefully they were from bacterial intrusion. The difficulty not easily set aside so small were the living in question and so universal is their dis tri but heir minute spores are readily borne from te place by currents of air, and every drop of teems with bacterial life. It was found, in course of time, that prolonged boiling uniformly effectual in destroying all germs, that nutrient material which had been exposed this treatment in flasks plugged with cotton could be kept for an indefinite period without putrefactive changes. The cotton-wool served the purpose of a filter, permitting inter of gases between the inside of the flask the outer world, but preventing any organisms the interior of the flask from outside. media which have thus been prevented putrefying are said to be “sterilised;” that remaining unchanged is due to the absence of life within them is easily shown by noting effect of introducing germs into them from Such sterile media are now largely emin studying the growth of bacteria, and 321 (298) Bacteria. ee ee when due precautions are taken it is not difficult to ensure securing what is called a ‘ pure cultivation” of a given organism; that is to say, one and only one kind of organism being introduced into the medium, there is a development within it of organisms of that kind and of that kind only. Thus the theory of spontaneous generation has been completely discarded; putrefactive proce es are now known to be due to the growth of bacteria, and by studying the differing ways in which different organisms affect nutrient material an invaluable means of cla ifying bacteria and of studying their life history has been placed at the disposal of bacteriologists.