477 
Table No. 19. — Milk from a healthy cow (No. 2), inoculated one and one-half 
hours after milking. 
[Controls, same milk heated to 100° C. in Arnold sterilizer for ten minutes. Organisms 
from 24-hour agar cultures, suspended in normal salt solution.] 
Bacteria 
per loop at 
once after 
milking. 
Bacteria per 
loop after 7i 
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 
9, 000 
B. lactis aerogenes in same milk undiluted 
6,000 
30,000 
B. lactis aerogenes (control, i. e., boiled milk) 
1,200 
(a) 
B. tvphosus in raw milk diluted with boiled milk as above (3+1) 
2,040 
2, 100 
B. tvphosus in same milk undiluted 
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 
1,320 
Staphylococcus pyogenes aureus in same milk undiluted 
1, 290 
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. 18 
there was a reduction of 96.6 p^r 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. 
These experiments were originally designed to demonstrate the 
presence of a germicidal substance in solution, but the results again 
show that the action is in part at least due to agglutination. As far 
as the restraining action is concerned, the results resemble a feeble 
antiseptic rather than a germicide. 
THE EFFECT OF HEATING AND FREEZING. 
The effect of heat varies with the micro-organism. The power to 
restrain B. lactis aerogenes is weakened and destroyed before that for 
typhoid. Thus, 55° C. for thirty minutes or 60° C. for twenty 
minutes markedly alters or destroys the power of milk to restrain the 
B. lactis aerogenes , while this degree of heat shows little influence as 
far as B. typhosus is concerned. 
Freezing milk for ten minutes apparently does not influence its 
germicidal power. Freezing the milk for forty-eight hours before 
inoculating it has no influence upon its restraining action as far as 
the typhoid organism is concerned, but apparently destroys this 
power for B. lactis aerogenes. 
