Armstrong – Table of Contents

same is true of those tissues which constitute the defense mechanism, wherever and
whatever they may be. It was therefore decided to determine whether a preliminary
immunization by the injection of a non-specific antigen might increase temporarily the
animal’s efficiency in its reaction against a subsequent inoculation with vaccine”. To test
this hypothesis, Armstrong planned to immunize mice against various antigens and
subsequently compare the number of deaths among previously immunized and non-
immunized groups following intra-cerebral inoculations with a virulent vaccine virus,
developed at the National Institute of Health, capable of producing a fatal encephalitis. A
dose of virus was selected that was slightly less than sufficient to kill all of a group of
normal mice. Diphtheria toxoid, broth and typhoid vaccine were used to make the
preliminary inoculations, and normal saline was used as the control material. Diphtheria
toxoid was used, however, in most of the tests for several reasons. Armstrong felt that it
was known to be an efficient exerciser of the “immune mechanism”. Also, if efficiency
could be demonstrated experimentally, it could be utilized in children by the simple
procedure of administering diphtheria immunization first, followed by vaccination
against smallpox, rather than in the reverse order, as was the custom in many United
States localities.
The mice were divided into groups and given two subcutaneous inoculations of
the test antigens. After appropriate intervals, the mice received various dilutions of the
vaccinia virus intra-cerebrally, and they were observed for 25 days. At the end of that
period the diphtheria toxoid immunized mice had a 27 per cent survival rate compared to
a 12 per cent survival rate for the control group. There were more survivals in the
diphtheria toxoid immunized groups than in the other groups and the toxoid treated mice