half-grown female, No. 947, were trapped on January 25 in the kitchen. Pooled tissues
from each of these mice produced transmissible infections in susceptible laboratory mice.
Dr. Charles Armstrong examining small rodents for signs of paralysis, in the old^
Hygienic Laboratory-NIH Building, probably around 1939. Courtesy of Mary Emma
Armstrong.
On the basis of the serological studies related to the two cases and their family
contacts, the isolation of virus from mice from the patients’ homes and the failure to find
infection in 21 mice trapped in 8 houses wherein human LCM cases did not occur,
Armstrong felt secure that the association between the human cases and the mice was
more than a coincidence. He believed that the mice constituted the source of the infection
for the following reasons: 1) In each instance the human case was ill in the home for only
4 days before being removed to the hospital; it would appear rather remarkable for both
cases to have infected the mice of their respective abodes. On the other hand if the