1914] 
NOLTE—SALIVARY ORGANISMS AND AIR POLLUTION 55 
evaporate. Then, 3 drops of mercuric chloride solution were 
applied and after 2 minutes washed off with distilled water. 
Following this, the preparation was treated with a few drops 
of 1 per cent acetic acid for 5 minutes, again washed in water, 
and finally stained for about 15 seconds with a few drops of 
gentian violet. After washing, and drying in the incubator at 
37° C., the vaseline was removed from the cover glass with 
xylene, and the preparation mounted in balsam and examined 
under the microscope. Тһе relation to Gram stain was observed 
on 2 and 4-day agar cultures incubated at 20°C. The prepa- 
rations were treated with aniline oil-gentian violet for 1% 
minutes, with Gram’s iodine solution for 13 minutes, and 
finally with 95 per cent alcohol for 3 minutes. The reactions 
are recorded as “— —" (decolorized in both tests), “+ —’’ 
(stained in one test and decolorized in the other), and “+ +” 
(stained in both tests). 
CULTURAL CHARACTERISTICS 
All cultural characteristics were observed in streak cultures 
on agar slants after 14 days’ incubation at 20°C., and 37°C. 
Such differences as developed between the cultures were 
almost entirely variations in color and vigor of surface growth. 
Under the latter, 5 types were distinguished as follows: 
1. Growth very faint and veil-like, or forming scattered 
translucent colonies. 
Growth better, but still meager. 
Growth good, but not abundant. 
Growth abundant. 
5. Growth very heavy. 
i oo bo 
In the study of chromogenesis, apparent differences in pigment 
production, due to unequal vigor of growth or evaporation, were, 
so far as possible, eliminated. This was accomplished by exam- 
ining in each case the same amount of material—a loopfull— 
spread evenly on white drawing paper having a rough surface. 
After drying at room temperature, the color of the pigment 
produced was compared with the colors as given by Ridgway’. 
1 Color standards and nomenclature. 1912. [Published by the author, Washing- 
ton, D. С.) 
