The number and distribution of micro-organisms in the air of the Boston City Hospital : with some carbonic acid determinations / by Greenleaf R. Tucker.

  • Tucker, Greenleaf R.
Date:
[1889]
Catalogue details

Licence: Public Domain Mark

Credit: The number and distribution of micro-organisms in the air of the Boston City Hospital : with some carbonic acid determinations / by Greenleaf R. Tucker. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    country, also, some new methods of culture have been prac- tised by the writer, in conjunction with Professor Sedgwick, in a series of investigations conducted at the Massachusetts Institute of Technology.** Hesse's Method. Hesse makes use of the fact previously ascertained,—that micro-organisms rapidly settle out in a quiet atmosphere. He employs a long glass tube of large bore, coated inside with sterilized nutrient gelatine. The tube is fastened to a photographic tripod in a horizontal position, and, by a suitable connection with two aspirator-bottles, a slow cur- rent of air (one litre in three minutes) is drawn through the tube. The germs are all supposed to settle out during the passage of the air through the tube, and remain fixed by the moist, solid gelatine, where they become visible after several days as isolated colonies. Frarikland's Method. This method consists in aspirating a known volume of air through a glass tube containing two sterile plugs of glass- wool alone, or glass-wool and fine sugar-powder ; after which the germ-laden filter is transferred to a flask containing melted sterilized nutrient gelatine, the two thoroughly shaken to- gether, and solidified upon the sides of the flask by cooling, where the colonies which develop can be counted. Petrie's Method. Petrie uses fine sand as a filter, packed in a small glass tube, and held in place by disks of wire gauze. After draw- ing through sufficient air by means of an air pump, the sand, with its occluded germs, is poured into several small double dishes of glass, containing nutrient gelatine, the object being to distribute the sand and germs over a considerable surface, so that the colonies may be more readily counted. The method employed in the present investigation was first used by the writer, in association with Professor Sedg- * See foot-note on page 164.