Bulletin Engineering Experiment Station Volume 55-64

Bulletin Engineering Experiment Station Volume 55-64

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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. 1919 edition. Excerpt: ...boiling water for a few minutes or brought to a boil over a fiame and if this treatment induces coagulation the reaction is considered as positive. If the milk has been over sterilized in the autoclave, coagulation does not take place as readily as when the medium is sterilized by the intermittent method in the Arnold. There is no digestion of the curd and the whey, if present, is clear. The litmus may be reduced by some strains. The milk reaction has been found very valuable in identification of the colon group. Gelatin liquefaction. The liquefaction of gelatin is an important test for the differentiation of colon species. Studies by Gligler and by Johnson and Levine indicate that this test is well correlated with motility and fermentation of glycerol. Unfortunately the liquefaction of gelatin is difficult to determine. The period of incubation usually employed is fourteen days at 20 degrees C. Gage and Phelps, and later Johnson and Levine pointed out that the proportion of liquefiers recognized varies with the period of incubation as may he seen from Table l. Among 202 strains studied by Johnson and Levine, 106 (52%) were gelatin liquefiers after 34 days incubation but only 31 (15.3%) showed this reaction in 13 days. TABLE I. LIQUEFACTION OF GELATIN BY 202 COLON STRAINS FROM SOIL. The long incubation period necessary makes this test an inconvenient one for practical work and in some laboratories a modification has been introduced employing 370 C. for?' 48 hours. This of course liquefieq the gelatin and so to determine whether a physiological decomposition has taken place the tubes are immersed in ice water until control tubes solidify. Inoculated tubes which remain liquid are regarded as having been peptonized by the action of the...show more

Product details

  • Paperback | 132 pages
  • 189 x 246 x 7mm | 249g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236761316
  • 9781236761316