(1932) were also concerned with staphylococci from milk.The present work has special reference to the food-poisoning substancewhich for convenience may be called "enterotoxin "-produced in culture by staphylococci of the cow's udder, or in milk or milk products naturally or artificially contaminated with staphylococci.With regard to cultural methods, Jordan (1930) found that enterotoxin was produced in plain infusion broth, pH 7-6, within 48 hr. at 370 C., while Jordan & Burrows (1934a, 1935 showed that larger amounts of it could be obtained by growing the organisms on 1-0% agar under CO2. Thus some strains which no longer produced enterotoxin in plain broth would still do so on the soft agar medium under C02, while some strains which formed no enterotoxin in the ordinary atmosphere would do so in an increased concentration of CO2. Twenty food-poisoning strains in their laboratory, however, lost their enterotoxic power in time even when grown by the CO2 method, but this power could be restored by a few transfers on a solid medium containing starch. In my experiments it was again found that under ordinary atmospheric conditions enterotoxin is formed in plain broth or in broth containing 5% sheep blood, but as a routine cultures were grown on 0.8% beef heart agar in Roux bottles incubated in an atmosphere of 20% C02. After 36 hr. at 37°C., 10.0 c.c. saline was added to the flask, and as much fluid as possible was pressed out of the agar through muslin, the fluid centrifuged and the supernatant passed through a small Berkefeld filter, after which, in order to destroy the a toxin which some strains produce in addition, the filtrate was placed in a bath of boiling water for 30 min. or
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