NEw York AGRICULTURAL EXPERIMENT STATION. III 
sary to pasteurize it at a comparatively low temperature, while to 
have the desired killing effect the milk must be held at the pas- 
teurizing temperature for a correspondingly longer interval. Ac- 
cordingly a different type of machine was required for this work. 
Since the cheapness and rapidity of action of the continuous flow 
machines are increased by running them at a lower temperature, 
the public easily confused the two types of machines. The attempt 
was generally made to use the continuous machines for pasteurizing 
milk for all purposes, running them at the low temperatures adapted 
to the other type. The results were bad from every point of view. 
Believing that the low temperature used would account for the 
poor results, a careful study was conducted of the germicidal action 
of a continuous pasteurizer when run at different temperatures.® 
This work showed that the temperature was really the keynote to 
the trouble. When the milk was pasteurized at 158° F. the killing 
action was quite variable and rarely well marked. When the tem- 
perature was raised to 178° I’. the destruction was so nearly com- 
plete as to leave little opposition to the germs to be later added in 
the starter. It was further shown that while pasteurizing at 185° 
F, did not produce a noticeably greater reduction in the germ con- 
tent it was not attended with any bad effects upon the butter. 
Since this latter temperature is sufficiently high to destroy the 
tubercle bacillus it was recommended for use where there was any 
danger of this organism being present in the milk. The general 
utility of pasteurization was shown so markedly while these ex- 
periments were being conducted that it has been used in our dairy 
continuously since that time. Its value in combating the spread 
of tuberculosis was well illustrated in our experience (see p. 112) 
with tuberculosis in our herd. When the presence of the disease 
was first detected all of our young stock was found to be infected, 
and the most probable explanation was a spread of the germs 
through the use of infected milk. After this date all of the milk 
which was fed to our calves was passed through the machine at 
185° F. Although twenty-five calves were thus raised upon the 
milk from tuberculous cows not one of them contracted the disease. 
TUBERCULOSIS IN CATTLE. 
Among the problems which have confronted the dairyman during 
the past quarter of a century none has presented greater difficulty 
* Bul. 172; same in Rpt. 18:127-149 (1899). 
