Abstract
Summary
A highly satisfactory and differential medium for the study of “S” and “R” forms of pneumococci is described. The medium consists of ordinary beef infusion agar pH 7.8 to which 5 to 10% defibrinated blood of the dog is added. To obtain the optimum result, the organisms are plated on such a medium and incubated for 16 to 18 hours. On examination with reflected light the “R” colonies present an extremely rough surface in distinct contrast to the smoothness of “S” forms.
Evidences point to the dog blood cells as furnishing the important constituent of such a medium.
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