5380 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1959 
antibody reaction, the technic has been extended to study sites of 
antibody formation. 
In simple terms, the tissue under study is covered by antibody-con- 
taining material, e.g., appropriate serum. Previously, the antibody 
was treated with a fluorescent dye. After a time the antibody is 
washed away. Since antigen will bind the specific antibody, fluores- 
cent material will remain fixed only at those locations where antigen 
is present. Many factors, such as polymerization and pH, affect the 
reaction and may alter the appearance under the fluorescence micro- 
scope. 
This method has been used by several workers for the demonstration 
of protein antigens, bacterial polysaccharides, viruses, rickettsiae, and 
plasma protein in tissues and cells. 
Plate 4, figures 14, demonstrate a technic for studying the distri- 
bution of nucleic acids in normal and virus-infected cells and have 
been supplied by Dr. Janet S. F. Niven and Dr. J. A. Armstrong, of 
the National Institute for Medical Research, London (17). The 
material, either fixed 3p sections or tissue-culture cells, is immersed in 
acid buffer (pH 2.7) and transferred to a 1: 2,000 solution of acridine 
orange in the same buffer for half an hour. After it is washed in 
buffer, the specimen is mounted, sealed to prevent drying, and ex- 
amined under the fluorescence microscope utilizing the blue-violet 
region of the spectrum. Structures containing DNA emit a bright 
greenish-yellow fluorescence, whereas RN A-containing material gives 
a flame-red color. 
FACTORS INFLUENCING VIRUS ACTIVITY 
We know that man has latent in various tissues throughout his 
body many viruses which were unknown to us a few years ago, but we 
do not know what many of these are doing there (18). We know that 
viruses can persist in their host for generations in either an infectious 
or a noninfectious form. They can mutate to form new strains and 
cause different disease symptoms. Viruses may have different effects, 
depending on the age, genetics, and state of nutrition and hormonal 
balance of the host (14). 
The conversion of a virus from a latent to an active state may be 
effected by seasonal factors. For instance, there is a tendency for 
polio to occur in the summertime or for sun and wind, somehow re- 
lated to the seasons, to influence the emergence of herpetic lesions. 
There are also hormonal factors, such as those associated with preg- 
nancy, that influence whether or not polio will result in a paralysis. 
Sometimes a bacterial infection can influence the conversion of 
latent virus to active virus (for example, the appearance of herpes 
simplex accompanying meningococcus meningitis or pneumococcus 
