2 BULLETIN 342, U. S. DEPARTMENT OF AGRICULTURE. 
pasteurization of milk, when the process is properly perfoumea 
affords protection from pathogenic organisms. Such disease-produc- | 
ing bacteria as Bacillus tuberculosis, B. typhi, B. diphtherie, and the a 
dysentery bacillus, when heated at 140° F. for 20 minutes or more, are 
destroyed, or at least lose their ability to produce disease. | 
According to Mohler (1),1 pasteurization offers protection against @ 
foot-and-mouth disease. He makes the following statement: “ Milk @ 
which has been pasteurized for the elimination of tubercle and — 
typhoid bacilli will not prove capable of transmitting the disease — 
[toot-and-mouth] to persons or animals fed with it.” In view of 
the recent outbreak of foot-and-mouth disease in this country this 
is of importance. | 
Within recent years several epidemics of septic sore throat have © 
been traced to milk. In some of these epidemics it was found possible @ 
by pasteurization to destroy streptococci which were isolated from 
throats of infected people and which were believed to be the infective | 
agents. Pasteurization, properly performed, seems to protect against © 
epidemics of this kind, but until the organism which causes the — 
clisease is definitely known it is impossible to say that it affords abso- — 
lute protection. | 
Epidemics of scarlet fever have been traced to milk supplies, and — 
in such cases pasteurization has been resorted to, with apparently 
satisfactory results, as a means of safeguarding the public health. | 
Pasteurization is of value from a commercial standpoint so far as | 
it increases the keeping quality of the milk and prevents financial — 
losses by souring. As practiced at the present time, commercial — 
pasteurization, with reasonable care, destroys about 99 per cent of © 
the bacteria, and while it does not prevent the ultimate souring of | 
milk, it does delay the process. At the present time pasteurization — 
is the best process for the destruction of bacteria in milk on a com- 
mercial scale. Many attempts have been made to destroy these bac- — 
teria by means of electricity, but its use commercially has not proved — 
satisfactory. Its action is usually indirect, the bacteria being de- | 
stroyed through the heat produced by the electric current or through | 
chemical substances produced by decomposition of the milk. It is | 
possible, however, that future research will develop some satisfactory | 
method of treating milk in this manner. | 
The use of ultra-violet rays for the destruction of bacteria in milk — 
hag aot proved to be of value as a commercial process. Experiments 
with these rays carried on by Ayers and Johnson (2) showed that 
while the rays cause great destruction of bacteria in milk, when 
exposed under suitable conditions, the process in its present state 
1 See references to literature at end of paper. 
