Présentation de l'éditeur
It is to be regretted that the tendency of investigation in bacteriology has been largely a study of effects, with little or no attempt to explain their fundamental causes. This is probably because the latter problems involve greater technical difficulties and offer less hope of immediate solution. Until a definite scientific foundation has been built up, however, on which to correlate the numberless already known facts, these will always remain isolated and to some extent unexplainable. Bacteria, like all living cells, produce changes in internal composition as well as in external environment by means of chemical reactions. Living protoplasm, in order to maintain its viability, is constantly abstracting certain essentials from its environment, and replacing them by other substances, while it is itself in a constant state of alteration. The changes wrought in the surrounding material by the presence of bacteria can only be definitely, that is chemically, followed by cultivating them upon media of known and exactly reproducible composition, the so-called synthetic media. Suitable media of this type are not easily developed, but work is in progress along this line which cannot fail to bring to light many significant and fundamental relationships. Changes within the bacterial bodies are even harder, if not entirely impossible, to follow completely. The present means which analytical chemists have at their disposal in the investigation of the most complicated of all known forms of matter are palpably imperfect. Bacterial changes, however, may be at times accompanied by (i) alterations in the empirical chemical composition of the whole bacterial bodies, and (2) alterations in the biological behavior of the organisms. Alterations in both these quanta are demonstrable, and can, at least in part, be correlated with their etiological factors.
(Typographical errors above are due to OCR software and don't occur in the book.)
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