A METHOD OF ANAEROBIC PLATING PER- 

 MITTING OBSERVATION OF GROWTH^ 



HORRY M. JONES 

 Research Laboratories of the Dairy Division, U. S. Department of Agriculture 



Because of the already numerous descriptions of methods 

 for growing cultures anaerobically, one hesitates to add another 

 method to the list without an apology. The method here 

 described will however be found of advantage in the isolation 

 of anaerobes from cheese, milk, soil or other material where 

 it is desired not only to secure growth of the anaerobes, but also 

 to obtain them in pure culture directly from the material under 

 examination. The method is chiefly to be recommended 

 because of the relatively small amount of inert gases necessary 

 to replace the air in contact with the media — an advantage 

 that will be appreciated in laboratories where generous supplies 

 of these gases are not available and where the method of anaerobic 

 plating is frequently employed on a small scale. Furthermore, 

 the rate and character of growth of the colonies are easily ob- 

 served from the beginning, so that it is not necessary to open 

 the anaerobic chamber at any time until sub-cultures are to 

 •be made. 



The apparatus consists of one half of a Petri dish sealed with 

 paraffine, of relatively low melting point, on a square stone or 

 metal base provided with an inlet for the inert gas and an out- 

 let for the displaced air. The base is conveniently made as 

 follows: Slabs of stone (such as Alberine stone, or soapstone) 

 or of cast iron, of about 2 cm. thickness, are cut in squares 

 about 1 cm. larger than the diameter of the Petri dish to be used. 

 Cut in one face of these slabs, with a lathe, an annular groove 

 3 mm. deep and 4 mm. wide, and of such a diameter that the 



^Published by permission of the Secretary of Agriculture. 



339 



