New Yorx AGricuLTuRAL ExpERIMENT Station. 141 
only acted as an insulator between the milk and the source of heat, 
but also encroached upon the interval between the revolving stirrer 
paddles and the wall, forming a rough surface along which the 
milk must pass. The fact that the machine was not permanently 
placed and lacked in rigidity was also a contributing factor to the 
above variations. 
Pasteurizing temperature.— As soon as the milk enters the bot- 
tom of the machine it takes up heat from the steam jacket and 
its temperature rises to the highest point just as it reaches the 
milk outlet. The temperature at this point is measured by a 
thermometer inserted in the outlet and constitutes the so-called 
“Pasteurizing Temperature,” although the milk really attained 
this degree only momentarily. As soon as the milk passes from 
the machine the temperature falls with a rapidity depending upon 
the surroundings. 
TAKING SAMPLES. 
The samples of unpasteurized milk were taken from the tem- 
pering vat after the milk had been thoroughly mixed. The only 
exception to this was during the earlier part of the work, when 
they were taken from the supply tank just before taking the 
samples of pasteurized milk from the machine. 
The samples of pasteurized milk were taken from the milk 
outlet after sufficient had passed to remove the effect of the bac- 
teria contained in the water used in starting the machine and in 
the machine itself. Care was taken to secure samples while the 
machine was running steadily at the desired temperature. 
The samples of about 150 cubic centimeters each in sterile 
flasks were set into a room at 1.5° to 4.5° C. (85°-40° F.) until 
the pasteurization was ended, when they were taken to the labora- 
tory on the floor above and the quantitative analyses made. 
BACTERIOLOGICAL TESTS. 
Method of dilution.— One ¢. c. of the unheated milk was added 
to 9 c. c. of sterile water and the two thoroughly mixed. This 
