110 “MARKET DAIRYING 
undesirable as compared with the “held” process. Be- 
sides the disease. bacteria mentioned on the chart, there 
are large numbers of other bacteria in milk some of 
which are even more difficult to destroy than the tuber- 
cule bacillus. These bacteria, while perhaps harmless 
to adults are known to have an irritating effect on the 
digestive system of babies and children. And because 
of these bacteria and as a matter of safety so far as 
bacteria in general are concerned, some of the leading 
city milk dealers have found it desirable to expose milk 
at 145° for an whole hour. These milk dealers have 
found it wise to pay less attention to the milk constituents 
and more to the bacteria. 
In the destruction of bacteria by the pasteurizing 
process, it is never safe to employ temperatures which 
closely approximate the thermal death point of those 
particular bacteria which it is desired to destroy. The 
ups and downs in the pasteurizing temperature, the in- 
accuracies in thermometers, and the changing conditions 
in the milk itself from one day to another, make it ad- 
visable to employ temperatures appreciably in excess of 
those absolutely necessary to destroy the bacteria un- 
der normal conditions. 
Milk that has been underheated is more dangerous than 
that which has not been heated at all. The reason for 
this is that inadequate heat in pasteurizing may destroy 
the lactic acid bacteria (which are easily killed) and by 
so doing actually better the conditions for the growth 
of the more resistant and obnoxious kinds. Lactic acid 
organisms are antagonistic to other classes of bacteria 
and are therefore a real safeguard to milk. This makes 
it plain that unless milk is pasteurized at a temperature 
which will destroy the pathogenic and non-acid bacteria 
