Encyclopaedia Britannica Volume 1

Encyclopaedia Britannica Volume 1

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1900 edition. Excerpt: ...of the fermentation they induce in attacking the tissues of the host, in which capacity they are "organic ferments." Some of the pathogenic forms attack but a single host, others (as Bacterium tuberculosis) can utilize a wide range of hosts. The chromogenic forms are readily recognized by the coloring matters they produce. The zymogenic forms are those which produce "inorganic ferments" (enzyms), which induce fermentation without themselves beingchanged. Upon the basis of oxygen supply, bacteria may be either aerobic or anaerobic, dependent upon their need of free oxygen or not. Certain bacteria can live without a supply of free oxygen if living in a solution in which they can produce fermentation; but if such is not the case, free oxygen must be available. Hence there are facultative and obligate aerobic and anaerobic forms; many of the pathogenic forms being facultative anaerobic fo rms. Notable among bacteria are those forms concerned in the process of "nitrification," and in the separation of sulphur and iron from watery solutions. The nitrifying bacteria change organic nitrogenous substances into soluble salts of nitric acid, thus performing an immense service in preparing the nitrogenous materials of the soil for absorption by plants, and in transforming into harmless and usable forms the nitrogenous wastes found in water. A striking expression of this work among the nitrogen compounds is to be seen in the niter or saltpeter beds. The sulphur-bacteria occur chiefly in waters in which hydrogen sulphid is being formed from the decay of plants and animals. The bacteria oxidize the hydrogen-sulphid and deposit masses of sulphur. The sulphur is then oxidized into sulphuric acid, which usually unites with...show more

Product details

  • Paperback | 652 pages
  • 189 x 246 x 33mm | 1,148g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236954998
  • 9781236954992