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more forms which have been studied and named, or designated by letters or figures or vernacular names, probably not one-tenth can be identified with any certainty owing to the meagerness of the descriptions. The older descriptions are particularly bad, and the effort to decide what was meant by these old names, for which somebody will by and by be strenuously claiming inalienable rights of priority, is usually time thrown away. There is quite enough to do in bacteriology, as every one knows who is dealing at first hand with its hard problems, without wasting precious energy in striving to guess what was meant by two and three line descriptions. All descriptions which do not describe, and there are many such, ought to be wholly ignored, and no species recognized as worthy of a place in literature unless so characterized as to be identifiable by others. A plea of this sort in the higher branches of botany or zoology would be a subject for laughter. Bad descriptions are however, so much the rule in bacteriology that it is no laughing matter but rather a great evil urgently demanding reform. It is a state of affairs which has come about naturally enough considering the way in which bacteriology has developed" but which would not now be tolerated for a moment in phanerogamic botany or in most branches of zoology and the continuance of which in bacteriology it is incumbent on every honest worker to limit and discourage in all pos
The best way in science, always, is to speak out plainly, and to join hands for the advancement of a good cause. Bad work should be ignored and “new species” relegated to limbo unless the descriptions conform to the requirements of modern bacteriological science, meaning by this expression the consensus of opinion among experienced and careful investigators everywhere. If there were some such agreement among the better class of workers, the improvement in systematic bacteriology would become very marked. The volume of publication would, indeed, decrease noticeably but this of itself would be a great advantage, and the quality of the work would more than correspondingly improve. Only in some such way can the strong tendency toward trashy publication be eliminated and light and order evolved from the present chaos.
12 About 650 species are mentioned in (11) Schizomycetacex, by de Toni and Trevisan in Saccardo's, Sylloge Fungorum, VIII, published in 1889, but this is not complete.
13 All the early systematists built upon a foundation of sand, i. e. uson pure morphology
With few exceptions, vegetable pathology seems to have been specially unfortunate in the class of persons who have devoted themselves to the study of bacterial diseases. While the bacterial side of animal pathology has had its Pasteur and Koch, its Esmarch, Hueppe, Flügge, Gaftky, Frænkel, Pfeiffer, Leffler, Duclaux, Metchnikoff, Chamberland, Roux, Welch, Sternberg, Smith, Prudden, and a host of other skilled experimenters, scarcely less eminent, and has made correspondingly great progress, the study of the bacterial diseases of plants has been principally in the hands of botanists without special laboratory training in bacteriology and even destitute in some cases of an elementary knowledge of right methods of work. The great development of modern bacteriology is attributable largely to the discovery that human diseases are due to these organisms, and to its consequent alliance with medicine, but there is no reason why the same rigid scrutiny of methods and sharp calling in question of statements which have led to such brilliant results in animal pathology in recent years should not be applied in the same way to vegetable pathology. Accurate experimentation and trustworthy results are from a purely scientific standpoint quite as desirable in one field as in the other.
Two things are especially to be kept in mind in describing any bacterial disease of plants : (1) The pathogenesis must be worked out conclusively; (2) If the organism is named, it must be so described that it can be identified by any competent bacteriologist no matter where it is found.
The four requirements under the first head, i. e. Pathogenesis, are now generally recognized to be as follows:
A. Constant association of the germ with the disease.
B. Isolation of the germ from the diseased tissues and study of the same in pure cultures on various media.
C. Production of the characteristic symptoms of the disease by inoculations from pure cultures.
D. Discovery of germs in the inoculated, diseased tissues, reisolation of the same, and growth on various media until it is determined beyond doubt that they are identical with the organism which was inoculated."
Not one of these steps can be omitted. Possible sources of error beset the investigator at every step, and anything short of a rigid demonstration cannot be accepted as proof. A. is usually quite easy, involving only the careful microscopic examination of abundant material, stained and unstained. was made possible by the improvement of methods, i. e. by the use of solid media, and especially by the discovery of the method of isolation by means of plate cultures. C. is quite easy, provided the right organism has been obtained and this be inserted into the proper tissues under the right conditions to insure growth. The fulfillment, however, of these conditions often involves long and vexatious delays, and taxes the acumen of the investigator to the utmost. D. serves as a check on all the preceding work, showing that there has been no unintentional mixing of organisms, and that the results obtained were actually due to the supposed cause. For the sake of brevity these four rules of practice will be referred to in the following pages simply as A. B. C. and D. What weight shall be given any specific statement depends of course on the reputation of the individual. Some men are so careful of their reputation and so little given to making unwarranted statements that their simple word goes a long way even when the statements themselves seem improbable, whereas the elaborate explanations of other men, if the asserted facts are at all out of the ordinary, have to be taken with a grain of salt.
The requirements under the second head, i. e. Description of the organism, are more numerous, and are embraced under two general divisions of very unequal value, namely Morpholoyy and Biology.
In the classification of the higher plants and animals morphology has been accepted from time immemorial as answering all the requirements of systematists, but such is far from being the case when it comes to the description of bacteria. These minute organisms, which are among the lowest and simplest forms of living things yet discovered by man, are, within the commonly accepted generic limits, so morphologically similar as very often to be indistinguishable with any certainty even under the highest powers of the microscope. As supplemental, therefore, to morphology, and even in many cases as a complete substitute for it, we must have recourse to Biology, viz. to the behaviour of the living organism under a variety of known, artificially prepared conditions, such for example as the peculiarity of its growth on various culture media, its thermal death point, its ability to ferment various sugars, the chemical products of its growth, its pathogenic power, etc. Morphologically identical organisms often differ so widely and constantly in their biological peculiarities that there can be no question about their being distinct species, or as to the real value of this means of classification. Probably it also has value, hitherto overlooked, for the differentiation of higher plants and animals, especially for determining the limits of polymorphic or closely related species.
14 A series of successful reinoculations is always very desirable and becomes indispensable in case the infections are obtained on plants grown in a locality where the disease prevails naturally. Of course, numerous un-inoculated plants, known as "checks” or “controls," must always be reserved for comparison.
It is not my intention in this place to mention all the biological tests which should be applied to any species for its proper characterization. These are being added to constantly by an army of trained workers in all parts of the world, and my own views of what is at present necessary, or at least highly desirable, will be sufficiently evident in what is to follow. Very likely, also, as knowledge increases, some of the tests which are now generally held to be important will be shown to have little specific worth.
This, however, appears to be a good place to insist on accuracy in all the details of bacteriological work, especially in the preparation of culture media, and on explicitness of statement so that other investigators may know just what was done and how it was done, and thus be able to repeat the experiment. When all details of work are suppressed the inference, naturally enough, is that the writer was ignorant or else that he desired to conceal something not specially to his credit, and which if plainly expressed might millitate against the value of his work. Either horn of the dilemma is equally bad. Some, however, who are desirous of doing good work in this field, or at least appear to be conscientious workers in other lines, do not seem to be aware of the necessity for extreme care in the preparation of culture media and the management of cultures. As a matter of fact, many bacteria are extremely sensitive to slight changes in the composition of the media in which they are grown or to other conditions within the control of the experimenter, and this appears to be true especially of the pathogenic species. Hence the many conflicting statements about the same organism. A few examples will render my meaning plainer. The careless exposure of cultures to bright sunshine may destroy the organism. An organism supposed to come from diseased tissues or from a culture, and which is being examined in a cover glass preparation, may have been derived actually from a contaminated staining fluid. The apparently simple matter of slightly unclean test tubes or flasks may lead to error, e. g. antiseptic influences may be at work, or preciptates may be thrown down and subsequently mistaken for bacterial growth. Some kinds of glass are unsuited to delicate bacteriological work, the culture fluids being contaminated by substances dissolved out of the walls of the beakers, tubes, and flasks. Tyros, of course, are liable to mistake almost anything for bacteria or to find them anywhere (See a long paper by Bernheim on (12) Die parasitären Bacterien der Cerealen, in Münch. med. Wochenschrift, 1888, pp. 743–745 and 767–770, and comments on the same by Buchner and Lehmann, Ibid., 1888, p. 906, and 1889, p. 110). Boiling culture media, after it has been compounded, in open beakers or in loosely plugged test tubes or flasks may unwittingly lead to its concentration. The use at different times of different peptones, or grades of gelatine, of unlike per cents of gelatine or agar, of varying grades of acidity or alkalinity, of impure chemicals, of different concentrations of the nutrient media, and of different methods in its preparation all tend to render comparative studies impossible. A large source of error in the differentiation of species by means of sugar fermentation experiments has been the employment of bouillon