A textbook of bacteriology : including the etiology and prevention of infective diseases and a short account of yeasts and moulds, haematozoa, and psorosperms / Edgar M. Crookshank.

  • Crookshank, Edgar M. (Edgar March), 1858-1928.
Date:
1896
Catalogue details

Licence: Public Domain Mark

Credit: A textbook of bacteriology : including the etiology and prevention of infective diseases and a short account of yeasts and moulds, haematozoa, and psorosperms / Edgar M. Crookshank. Source: Wellcome Collection.

    191/845 (page 142)
    The emptying continues by siphon action, and air is drawn in along the cylinder to replace the water. When the upper flask is empty, the position of the two is reversed, and the flow again started. When a sufficient volume has been drawn through the cylinder, the outer cap and the cotton-wool plug are replaced, and it is set aside for the colonies to develop. As an example, twenty-five litres of air from an open square in Berlin gave rise to three colonies of bacteria and sixteen moulds ; on the other hand, two litres from a school- Fig. 71.—Hesse's Apparatus. room just vacated by the scholars gave thirty-seven colonies of bacteria and thirty-three moulds. Porous substances, such as sand, powdered glass, or sugar, may be used for the filtration of samples of air; and an apparatus is employed in a convenient form to be conveyed to the laboratory for the subsequent examination. Petri's Apparatus consists of a glass-tube 9 cm. long, containing two sand-filters separated from each other. A known volume of air is aspirated through the tube. The bacteria are arrested and can