ON THE AMOUNT OF CARBON DIOXIDE SUPPLIED FOR THE PRI- MARY ISOLATION OF NEISSERIA GONORRHOEAE

The importance of increased carbon dioxide tension for the primary isolation of Neisseria gotorrhoeae is well recognized. Some of the methods advocated for increasing the carbon dioxide in the atmosphere in which the cultures are to be incubated are (1) replacing about 10 per cent of the air in the container with carbon dioxide from a tank, (2) mixing measured amounts of sodium bicarbonate solution and dilute sulfuric acid so as to obtain the desired volume of carbon diox-ide, (3) placing a lighted, smokeless candle in the container with the cultures before closing the container, and (4) placing a handful of moistened oats in the container with the cultures before closing the container. To our knowledge and experience, all of these methods are satisfactory for supplying the necessary carbon dioxide in the environment in which the cultures are to be incubated. The first method cited supplies more carbon dioxide than is necessary. The work of Ferguson (1945) supports that conclusion as he found that strains of the gonococcus grew "equally well on 'chocolate ' agar in a zone of carbon dioxide enrichment with a lower limit between 2 and 2.3 per cent and a