v ] METHODS OF INOCULATION. 33 



A method which is very useful is the one recommended by 

 Cohn and Miflet. 1 The principle of it is, that by means of an 

 aspirator, an air-pump of any kind e.g. a Sprengel pump, or 

 simply the fall of water air of a particular locality is drawn 

 into one, two, or more Wolffs bottles (each with the ordinary 

 two bent glass tubes), connected with one another by short 

 pieces of india-rubber tubing, and containing the sterile material 

 in which the organisms are required to grow. All bottles and 

 tubes being of course sterile, the plugging of the tubes after 

 the air has passed is done with sterile cotton-wooL Any quan- 

 tity of air for any length of time can thus be passed through 

 a series of such bottles, the one that receives the air first being 

 of course most contaminated. 



The bottles are after the experiment placed in the incubator 

 if required, the outer end of their tubes being plugged with 

 cotton-wooL 



Miquel 2 has carefully described many ingenious methods 

 for the study of air-organisms 



1 Zeittchr. f. Biol d. Pfl. Hi. 1, p. 119. 



" Les Organismes vivants de V Atmosphere, Paris, 1883. 



