A manual of bacteriology, clinical and applied / by Richard T. Hewlett.

  • Hewlett, R. Tanner (Richard Tanner), 1865-1940.
Date:
1902
Catalogue details

Licence: Public Domain Mark

Credit: A manual of bacteriology, clinical and applied / by Richard T. Hewlett. Source: Wellcome Collection.

    40/626 (page 24)
    the culture may be distilled; the first 20 c.c. of the distillate will contain the bulk of the indol. This 4 indol-reaction ’ is not necessarily always due to indol; the writer has shown 1 that the indol-like reaction obtained with cultures of the diphtheria and pseudo-diph¬ theria bacilli is owing to the presence of skatol-carboxylic acid. This substance is distinguished from indol by being non-volatile. To make sure of the presence of indol, the culture should therefore always be distilled. Another important series of changes is that included under the term ‘ nitrification.’ As mentioned before, proteid, albuminoid, and other complex nitrogenous matters and urea, all of which are valuable manures for plant life, cease to be so unless bacteria are present. Through the agency of the putrefactive bacteria am¬ monia compounds are ultimately produced from the more complex nitrogenous substances. In order, however, that plants may obtain their requisite nitrogen, the nitrogen must be in the form of nitrates. Although so important, extremely small quantities are present in the soil; in fertile soils, for example, under some conditions there may be as little as one part of nitrogen in 1,000,000, and there is often less than ten parts. The bodies yielding nitric acid in the soil a-re: (1) free nitrogen, (2) small quantities of nitrates in rain-water, (3) ammonium salts, applied intentionally or carried to the soil by rain or derived from the decay of organic matter, (4) various nitrogenous organic substances arising from the decay of animal and vegetable matters. With regard to the production of nitric acid from nitrogenous organic matters very little was formerly known. In 1877 Schloesing and Muntz by an ingenious experiment showed that nitrification (as the production of nitric acid is termed) of nitrogenous organic matter is brought about by 1 Trans. Path. Soc. Land. LII, pt. ii. 1901, p. 113.