Armstrong – Table of Contents

virus by injection into the spinal canal (intrathecal route), into the veins (intravenous),
into the abdomen (intraperitoneal) and into the windpipe (intratracheal). When inoculated
by each of these routes, monkeys became ill, recovered, then failed to react when
challenged by intracerebral injection with live virus indicating the acquisition of
immunity to the virus.
The major feature that distinguished this new virus from St. Louis encephalitis was the
microscopic pathologic anatomy described in detail by Dr. Ralph D. Lillie (21). As
described: In the majority of the monkeys there was more or less diffuse and irregular
cellular infiltration of the meninges (membrane coverings of the brain). Usually the
exudate was composed chiefly of small lymphocytes. In most animals there was a more
or less pronounced swelling, edema and lymphocytic infiltration of the choroid plexi (the
cellular membrane lining the intracerebral ventricles). Often the two layers of the plexal
epithelium were separated by dense masses of lymphocytes of such magnitude as to
enlarge the plexal villi four to six times. Scattered areas of lymphoid infiltration and focal
areas of intracerebral pathology occurred elsewhere, but the major foci of lymphocyte
infiltration in the brain meninges and choroids plexus determined the descriptive naming
of this infection as lymphocytic choriomeningitis.
The mystery surrounding the discovery of this new virus was its origin.
Armstrong speculated as follows: “It is not obvious whether this virus came from Case C.
G. or from one of the monkeys used in the transfer of virus from the case. In either event
the virus was apparently present in a latent state and was activated during successive
transfers.