PASTEURIZATION 211 
ture of 70° C. (158° F.) for their destruction, and some 
will even survive boiling. ‘Therefore, there is no cer- 
tainty that all toxins which may be present in milk will 
be destroyed even if the milk is boiled. While there 
is no direct proof that milk containing toxins is injurious 
to health, at the same time we are also without positive 
knowledge that such milk is harmless (see page 45). 
Although there is no definite information regarding 
the effect of heat upon the cleavage products resulting 
from the breaking up of the milk constituents by bac- 
teria, we have reason to believe that they are not all 
destroyed by heat. This is an important point because 
some of these substances are of a harmful character. 
In the light of our present knowledge regarding the 
effects of pasteurization upon toxins and cleavage prod- 
ucts, it would seem advisable to limit the production of 
these substances as much as possible by protecting the 
milk from bacterial contamination and by promptly 
cooling it and keeping it cool until it is pasteurized. There 
should be a limit to the number of bacteria which may 
be present in milk which is to be pasteurized, and this 
limit should be as low as circumstances will permit. 
4. Nutritive Properties—The statement is fre- 
quently made that milk may be heated at 145° F. (62.8° 
C.) for thirty minutes without affecting its nutritive 
properties, but this is not confirmed by the experience 
of Hess, who saw scurvy develop in from two to three 
months in nearly every one of a group of infants who 
were being fed on milk pasteurized in that manner; when 
orange juice or potato water was added to the milk the 
disease was cured. The observations of Plantenga indi- 
cate that this diseased condition is not due entirely to 
the effect of heat on the milk. He reports that while 
