Cultures of microorganisms similar to those described by Evans have been obtained in media inoculated with suspensions of herpes virus-infected brains prepared by grinding. But they have also been isolated from saline suspensions of uninoculated meat particles ground in a sterile mortar, and from dextrose broth treated in the same way. It is believed that these organisms are contaminants introduced during the process of grinding. Since they enter the material in no great number, one may suppose them to be suppressed by animals inoculated with the ground substance. In artificial media, on the other hand, they find favorable conditions for multiplication. In our experience, no growth of microorganisms is obtained in routine cultures of virus-infected brains, when fragments, instead of ground material, are used—a fact which may be taken to support the explanation just given.
The tests of the part played by streptococci in experimental virus encephalitis failed to disclose that the microorganisms have any etiological relationship to the affection. The intracerebral injection of rabbits with the cultures procured in the course of the experiments produces a purulent type of meningoencephalitis which does not resemble virus encephalitis either in its symptom-complex or in its pathology. The same type of meningitis follows the injection of streptococci derived from ground meat particles, from "ground" broth, from normal brains, and those infected with herpes virus. Some rabbits manifested resistance to the streptococci, whereas all that have been inoculated intracerebrally with the three strains of herpes virus used in this study have proved susceptible thereto. Certain of the rabbits just mentioned which had proved resistant to streptococci inoculated into the brain or cornea were injected with herpes virus and reacted typically. Comparative tests have revealed that the streptococci are more sensitive to the destructive effect of 50 per cent glycerol than is herpes virus. From all this, it can be concluded that streptococci are not the visible form of herpes virus, nor do they produce in rabbits effects like those induced in the brain and cornea by the herpes virus.