667 
Test No. B with Freeman’s Pasteurizer. 
Temperature of milk, 11° C. 
Temperature of water in jacket, 22° C. 
Temperature of milk — ° c. 
Five minutes after immersion in boiling water ^ 50 
Ten minutes after immersion in boiling water 63 
Fifteen minutes after immersion in boiling water 66. 6 
Twenty minutes after immersion in boiling water 67. 5 
Twenty-five .minutes after immersion in boiling water 67. 7 
Thirty minutes after immersion in boiling water 67. 4 
Thirty-five minutes after immersion in boiling water 67 
Forty minutes after immersion in boiling water 66. 6 
Forty-five minutes after immersion in boiling water 66 
It took thirteen minutes in running tap water, at 22° C., to cool the milk to 
30° C. 
Whole time, forty-five minutes. 
Above 65° C., thirty minutes. 
Bacteria per cubic cen- 
timeter.a 
Raw milk. 
After pas- 
teurization. 
Milk from — 
Dairy A 
1.900. 000 
2. 500.000 
2. 100.000 
440.000 
1.090.000 
29, 800, 000 
1.420.000 
590.000 
300 
500 
50 
None. 
200 
1,750 
None. 
2,650 
Dairy B 
Dairy C 
Dairy D ; 
Dairy E 
Dairy F 
Dairy G 
Dairy H 
“Colonies on agar plates after twenty-four hours’ incubation at 37° C. 
Note. — Recently (November, 1907) Freeman has modified his pasteurizer so that the 
milk is heated to 60° C. for forty minutes. (See his article on “ The ferments in milk and 
their relation to pasteurization,” in the Jour, of the Amer. Med. Assn., Nov. 23, 1907, Vol. 
XLIX, No. 21, p. 1740.) 
Milk is frequently pasteurized by simply placing the bottle of milk 
as it is received in a pot of water, the water boiled for a variable 
length of time, and then cooled. As will be shown by the following 
experiments, this is not always an entirely safe procedure for the 
purposes of home pasteurization. The depth of water in which the 
bottle is immersed markedly affects the results. The neck of the bot- 
tle must always project above the water, and unless the pot has a lid 
the upper layers of the milk may escape heating, especially if the 
contents have not been well shaken up and the thick cream, which is 
in part turned to butter as a result of agitation on the delivery wagon, 
prevents circulation of the fluid. 
It will be seen in some of the experiments made by myself in the 
Hygienic Laboratory that, contrary to what might be expected from 
