(Уот 1 
72 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
the 11 cocci present, therefore, two were of the characteristic 
salivary type, and as only one-third of the sample was plated, 
a total of 6 may have been present in the entire volume of air 
examined, or a frequency of occurrence of 1 in 1,800. Accord- 
ing to table vr, the sanitary quality of the air was ‘probably 
unsafe." 
Experiment 5.—During the sampling process for this experi- 
ment, 44 persons were seated and approximately 30 standing. 
Of the 26 colonies which developed on plate 5 (see table rx), 
14 were of bacilli, 2 of streptothrix, and 10 of cocci. When 
transferred to the three differential media, all of the latter gave 
negative reactions, indicating that the air in the car at the time 
of this experiment was ''safe." 
Experiment 6.—At the time of sampling, 44 persons were 
seated and 30 were standing. Оп account of the large number 
of colonies present, only a representative sector of plate 1—com- 
prising one-twelfth of the total area—was examined (see table тх). 
On this area 21 colonies were counted, 5 bacillus and 16 соссив. 
On the three differential media, 4 of the latter gave nega- 
tive reactions throughout, 6 were negative on lactose and milk 
but positive on saccharose, and 6 gave positive reactions on all 
three media. It follows that 6 salivary cocci were isolated from 
one-twelfth of the plate, making a total of 72 from the entire 
plate, or of 1,080 from the total volume of sand solution,—a 
frequency of occurrence of 1 in 10. According to table vr, the 
air in the car at the time of the experiment was ' unsafe." 
Experiment 8.—The number of persons seated and standing 
was the same as in experiment 6. Оп the plate examined (see 
table rx), 34 colonies developed—15 bacillus and 19 coccus. Оп 
the three differential media the coccus forms reacted as follows: 
Twelve gave negative reactions throughout, 6 were negative 
on lactose and milk but positive on saccharose, and 1 was nega- 
tive on lactose and saccharose but positive on milk. The 
last form was found, after again staining with gentian violet 
and examining under the microscope, to be a short bacillus. It 
is to be noted that 6 organisms of the unidentified coccus type 
were again present. No characteristic salivary cocci were 
present, thereby marking the air of this particular car as “safe” 
at the time of the experiment. 
