The fact that certain species of bacteria have an inhibiting effect on the development of other species or varieties is too well known to need discussion. This effect is frequently observed on agar plates on which the development of the colonies of one species may be restricted or completely suppressed by a preponderance of colonies of another variety. Marmorek (1902) has shown that a broth in which a hemolytic streptococcus has grown is unfavorable to the growth of this same organism or to that of any other hemolytic streptococcus. McLeod and Govenlock (1921) have demonstrated that pneumococci inhibit such bacteria as coli, dysentery, and staphylococci, as well as other pneumococci, and that this inhibiting property may be destroyed by heating the cultures to 85°C. Gundel (1927) found that coli not only inhibited the growth of anthrax but under certain conditions completely destroyed it. He also found that this effect could be prevented by shaking the culture with such adsorbing materials as kieselguhr, charcoal, etc. It is usually assumed that the lactic streptococci and bulgaricus, which differ in their action on milk in degree rather than in kind, grow together satisfactorily and even have a mutually favorable action. However, if a bulgaricus culture is used to increase the acidity of ordinary buttermilk the action is slow and may even fail entirely. If milk is inoculated with equal quantities of lactic' and bulgaricus cultures or only slightly predominating

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