46 
Russell and Hastings,® 1904, had worked previously from the 
standpoint of a comparatively low temperature, 60° C. They now 
worked from the standpoint of a short exposure, such, for instance, 
as is available in a continuous-action pasteurizing machine, to deter- 
mine how low a temperature could be safely used with such neces- 
sarily short exposures. Milk infected with human and bovine cul- 
tures of known origin and virulence was exposed in sealed glass tubes 
placed in a water bath. It took three-fourths of a minute for the 
contained milk to reach the temperature of the outside water. 
Virulence was determined upon guinea pigs by the intraperitoneal 
method. 
Their results show that material exposed to 160° F. (71.1° C.) for 
one minute was freed of living tubercle bacilli. This applied to a 
very virulent bovine strain as well as to less virulent bovine and 
human strains. The authors conclude that 71.1° C. or more for a 
period of one minute suffices to destroy the virulence of bovine 
tubercle cultures so that the disease is not produced in guinea pigs 
inoculated with amounts of the cultures ranging from 2 to 5 milli- 
grams. As definite amounts of the culture had been added to the 
milk, the dosage of each animal could be approximated. It is fair 
to note that the virulent bovine strain produced lesions in animals 
receiving the heated milk, which, however, were justly regarded by 
the authors as being due to dead bacteria, since animals inoculated 
with this material failed to develop tuberculosis. The authors do 
not unreservedly recommend this temperature and exposure for 
routine practical pasteurization without further investigation under 
all conditions. 
Schwellengroebel, ^ 1904, shows that when milk is pasteurized in 
bottles the tubercle bacilli, if present, may be protected against the 
heat by (1) the rough or cracked surface of the rubber washers used 
by some dairymen in closing the bottles, (2) the dried layer of milk 
in improperly cleansed bottles, (3) the pellicle formed on the surface 
of heated milk, and (4) the foam formed in the same way. The reme- 
dies are, of course, sterilization of bottles, washers, etc., and heating 
under conditions which prevent the formation of foam and pellicle. 
Zelenski,^ 1906, is a recent advocate of higher temperatures in the 
pasteurization of milk. He finds that 76° for ten, fifteen, or twenty 
minutes is insufficient to kill the bacilli. 
« Russell, H. L., and Hastings, E. G. : Effects of short periods of exposure to heat 
on tubercle bacilli in milk. University of Wisconsin Agricultural Experiment Sta- 
tion, 21st Ann. Rep., 1904, p. 178. 
b Schwellengrobel, M. : Ueber das Pasteurisiren der Milch. Cent. f. Bakt., Abt. 2, 
vol. 12, 1904, p. 440. 
cZelenski: Zur Frage der Pasteurisation der Sauglingsmilch. Jahrb. f. Kinder- 
heilkunde, 1906, vol. 63, 3, p. 288. 
