The biological examination of water / by C.J.H. Warden.

  • Warden, Charles James Hislop, 1851-1900.
Date:
1885
Catalogue details

Licence: Public Domain Mark

Credit: The biological examination of water / by C.J.H. Warden. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    quently conveyed by water. The addition of one drop of a cholera stool to a litre of sterilised water would form a mixture which, if examined by the Wanklyn, Frankland, or any other chemical method, would yield absolutely negative results. The analysis of a stronger mixture would show the presence of so much “ free ” and “ albu- menoid ammonia,” or “ organic” carbon and” nitrogen,” but beyond that no information would accrue. The bacte- riological examination would, on the other hand, in either case, with absolute certainty demonstrate the presence of a comma-shaped micro-organism, while subsequent culti- vation experiments would indicate whether the organism was the cholera bacillus or not. I do not wish it to be understood that I consider the chemical examination of a potable water useless : the badteriological test is not by any means intended to supersede chemical methods ; it is only an additional test, but one supplying information which a chemical analysis does not afford. ^ Briefly, Prof. Koch’s method consists in adding a mea- sured volume of water to sterilised liquid meat peptone gelatin, which is then poured on a glass plate, and after a certain period the developed colonies of micro-organisms counted, examined microscopically, and, if necessary, cultivated in various media and under different physical conditions. In describing the method I propose first giving a list of the apparatus required ; (2) method of preparing the reagents; (3) precautions to be adopted in the colledtion of samples of water ; (.]) analytical process ; (5) inferences to be drawn from the results. I. Description of Apparatus. The apparatus used for the badteriological examination of water are simple, and with a few exceptions are to be found in every chemical laboratory. The only expensive instrument is the microscope; the remainder are all in- expensive. Test-tubes.—The most suitable size is 160x15 m.m. The tubes are employed for containing the gelatin solu- tion, and are prepared for use in the following manner :— They are tinsed with a small amount of strong hydro- chloric acid, and thoroughly washed with water, care being taken to remove all trace of acid. The tubes are inverted, and allowed to drain and dry. When quite dry they are plugged moderately tight with cotton-wool. The plug should extend about three-quarters of an inch within, and the same distance beyond the mouth. The tubes are then packed in a wire basket (Fig. 1), with the plugged mouths upwards, and placed in a hot-air bath (Fig. 2),