468 
THE EFFECT OF DILUTION. 
Whole raw milk from a healthy cow (No. 2) was diluted in the 
proportion of 1 volume of milk to 3 volumes of distilled water. 
Inoculations were made two hours after milking. Twenty-four-hour 
agar cultures used. 
Table No. 17. 
[ 
Bacteria 
per loop at 
once after 
inocula- 
tion. 
Bacteria per loop after 
10 hours at 37°C. 
Culture 
Tube vigorously 
shaken 1 a g itated 5 
1 minutes 
«**■' a “ d 
pipette. 
B. typhosus in diluted milk (1+3) J ! 
11,000 
3,000 | 25,000 
B . t yphosus in same milk undiluted 
35,000 
1,200 ■ 15,000 
B. typhosus in sterilized milk (control) 
16,000 
ab 160,000 ! 
B. lactis aerogenes in diluted milk (1+3) 
3,000 
4,000 67,000 
B. lactis aerogenes in same milk undiluted 
5,400 
33 92 
B. lactis aerogenes in sterilized milk (control) 
36,000 
a b 360,000 
a Innumerable. 
b About. 
Table No. 18 . — Milk from a healthy cow (No. 2), inoculated 1\ hours after milking. 
[Controls, same milk heated to 100° C. in Arnold sterilizer for 10 minutes. Organisms from 24-hour 
agar cultures, suspended in normal salt solution.] 
Bacteria 
per loop at 
once after 
milking. 
Bacteria per 
loop after 7\ 
hours at 37° 
C. Tube 
shaken mod- 
erately. 
B. lactis aerogenes in raw milk diluted with same milk boiled (raw 3 parts, 
boiled 1 part) 
1,460 
6,000 
9,000 
30,000 
B. lactis aerogenes in same milk, undiluted 
B. lactis aerogenes (control, i. e., boiled milk ) 
1,200 
(a) 
B. typhosus in raw milk diluted with boiled milk as above (3+1) 
2,040 
2, 100 
B. typhosus in same milk, undiluted _ i 
1,680 
2, 340 
B. typhosus (control, i. e., boiled milk) 
2,160 
(°) 
Staphylococcus pyogenes aureus in raw milk diluted with boiled milk as 
above (3+1) 
1,060 
1,530 
Staphylococcus pyogenes aureus in same milk, undiluted 
1,290 
1, 320 
Staphylococcus pyogenes aureus (control, i. e., boiled milk) 
2,660 
30,000 
Original milk 
3 
430 
a Innumerable. 
Dilution has an appreciable effect. For instance, in Table No. T7 
there was a reduction of 96.6 per cent in the number of colonies of 
typhoid in whole milk, but only 73 per cent in the diluted milk. A 
similar effect is shown in relation to B. lactis aerogenes. 
