THE CYPHOID FLY, OB BOUSE FLY. 
Table 111. Sources of bacteria from flies. 
29 
Total Total acid 
lumber. bacteria. 
1807. 
July 27 
July 27 
Aug. 6 
A.m.! I 
a.ug.14 
Sept i 
Bept.21 
8ept21 
Bept.27 
A.ug.20 
i. l fly, bacteriological 
laboratory 
[b) l fly, bacteriological 
laboratory 
id 19 cow stable flies 
Average per fly 
swill-barrel flies.... 
Average per By 
(t) Ml pigpen Hies 
Average per fly 
/) 18 swill-barrel flies.... 
Average per fly 
[g] 80 dwelling-house flies. 
A\ erage per By 
(h) 26dwelling-house flies. 
Average per fly 
i no dwelling-house flies. 
Average per fly 
tj) l large bluebottle 
blowih 
3, 160 
550 
,980,000 
420,000 
,000,000 
,660,000 
,000,000 
928,000 
sun. i inn 
.inn. (MM) 
126,000 
17,680 
880, 
880, 
600, I 
322,700 
308. 700 
Total average of 41 1 flies.. 1,222, 570 
Average per cent of n I 
flies 
Average per fly of 256 
flies, experiments (d), 
(< i, and (/) 3,0(51,000 
Average per cent of 256 i 
flies, experiments (d), 
'V and (/ i 
LOO 
in >i> 
600 
mm 
800 

Tim 
I 
ooo 
000 
I C7 
ooo 
nun 
(Mill 
200 
Rapid 
Slow 
liquefy liquefj 
mil- bac oil; bac 
teria. teria. 
lactw 
Group \. 
Group \ 
Class 2. 
nun 





100,000 
700 
I) 



120,000 
1,600 
\Mn. 
Ni.:;nn 
I uu 

20,000 
I. nun 


266,000 
I. 150 
i i. ioo ooo 
804,1 
L2.600 
117 
34, I 
L,300 
125,000 
I. inn 
16,000 
1,631 ' 
19,300 
1, 176,000 
12,200 
30,000,000 
367, 300 
30 
165, 000 
7 830 
230 
268,700 
18 
" 2,200 mold spores. 
" From the above table the bacterial population of 414 flies is pretty 
well represented. The domestic fly is passing from a disgusting nui- 
sance and troublesome pest to a reputation of being a dangerous 
enemy to human health. A species of mosquito has been demon- 
strated to be the cause of the spread of malaria. Another kind of 
mosquito is the cause of yellow fever, and now the house fly is con- 
sidered an agency in the distribution of typhoid fever, summer coin- 
plaint, cholera infantum, etc. 
"The numbers of bacteria on a single fly may range all the way 
from 550 to 6,600,000. Early in the fly season the numbers of bac- 
teria on flies are comparatively small, while later the numbers arc 
comparatively vvvy large. The place where flies Live also determines 
largely the numbers thai they carry. The average for the 11! flies 
was about one and one-fourth million bacteria on each. Il hardly 
seems possible for so small a bil of* life to carry so large a number of 
organisms. The method of the experiment was to catch the flies from 
the several sources by means of a sterile fly net, introduce them into 
a sterile bottle, and pour into the bottle a known quantity of steril 
ized water, then -hake the bottle to wash the bacteria from their 
bodies, to simulate the number of organisms that would come from a 
fly in falling into a lot of milk. In experiments '<L' ' < .' and ■ /' " 
