Extracts from the annual report of the medical officer of the Local Government Board for 1884. Disinfection by heat. / being a report by H. F. Parsons.

  • Parsons, H. F.
Date:
1886
Catalogue details

Licence: Public Domain Mark

Credit: Extracts from the annual report of the medical officer of the Local Government Board for 1884. Disinfection by heat. / being a report by H. F. Parsons. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

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    On Disinfection by Heat; by Dr. Parsons. Experiments with moist air. Results of ex- periments with dry heat on anthrax bacillus ; Without spores. With spores. together forming one chamber, which was wrapped in flannel to keep in the heat. Through the hole in the bottom of the uppermost pot the materials to be. subjected to heat were let down, and suspended by wires at a depth of six inches from the top, a thermometer (not registering) being inserted in the hole in such manner that its bulb was in proximity to the suspended objects. By watching this thermometer and regulating the supply of gas, or by the use of a Bunsen thermo-regulator, the temperature of the chamber could be maintained within a variation of a few degrees. In view of the superior efficacy of steam, to be hereafter spoken of, both in the destruction of infective matters and in the penetration of badly conducting materials, some experiments were made with hot moist air in the hope that it might be found possible to obtain the advantages of the use of steam without its drawbacks. This hope, however, was not realised, it being found by Dr. Klein that the spores of the bacillus anthracis at all events retained their vitality equally well in heated air, whether this were dry or moist. In these experiments either a saucer of water, replenished from time to time through a long funnel, was placed at the bottom of the middle pot in the above arrangement, or steam evolved in a flask was led into the chamber by a pipe. An attempt was made to measure the degree of humidity of the air in these experiments by suspending in the chamber two maximum- registering thermometers arranged side by side, one of them having its bulb covered with gauze kept moist by dipping in a phial of water, as in the wet-and-dry-bulb arrangement employed by meteorologists. I find, however, that there are no tables or formulas in existence by which the degree of humidity of the air corresponding to a given difference between the wet and dry bulb thermometers at these high temperatures can be ascertained. I am informed also that the conditions in a heated chamber are so different from those met with in meteorological practice, and there are so many sources of error affecting the readings, that it is doubtful whether the relative humidity of the air could with any degree of accuracy be obtained in this way. The following are the results of the inoculations made by Dr. Klein with infected materials heated in air :— A.—Experiments with Anthrax. 1. Blood of Guinea-pig, dead of Anthrax, exposed on Strips of Flannel to Dry Heat of 212°-218° F. for the following periods:— Duration of Animals Exposure. Inoculated. Result. (a.) For 1 hour, 1 guinea-pig 1 Reinaiued welL (w.) For 5 minutes ditto J 2. Spores of Anthrax Bacillus, exposed on Strips of Flannel to Dry Heat of 212°-218° F. Animals Duration. Inoculated. Result. For 5 minutes, For 1 hour guinea-pig J ditto | [Died of typical anthrax with- in 48 hours, (b) a few hours after (a). For 2 hours ditto Do. after 48 hours. Vu.., For 4 hours ditto Remained well. N.B. (c) and (d) were heated in a water-bath, the outer chamber of which contained a saline solution boiling at 220° F. («•) (*■) (*> (d.)