124 PRINCIPLES AND PRACTICE OF MILK HYGIENE 
throat occurring among dairy workers or in their fam- 
ilies; if persons who have attended diphtheria patients 
or individuals recovering from the disease are not per- 
mitted to handle milk or milk vessels until cultures from 
the throat prove to be free from the bacilli, and if re- 
turned bottles are sterilized before refilling. Frequently 
the bacilli are not very virulent. 
The diphtheria bacillus has been demonstrated in 
niilk only a few times, principally because the organism 
is present in infected milk in small numbers and usually 
for only a short period. There is no doubt, however, of 
its transmission by milk. The milk is not changed in 
appearance by the growth of the organism. The bacillus 
is not affected by the degree of acidity present in cream 
ripe for churning, and it may therefore be present in 
butter and also in other dairy products, although we have 
no reports of the latter carrying infection. A compara- 
tively low degree of heat is sufficient to destroy the 
organism. Itis usually killed by a temperature of 55° C. 
(131° F.), but occasionally some individuals survive 
until the temperature reaches 60° C. (140° F.). 
When an outbreak of diphtheria occurs with the 
characteristics of a milk-borne epidemic, the same pro- 
cedure should be followed as described under typhoid 
fever. 
SEPTIC SORE THROAT - 
Epidemics of septic sore throat originating from in- 
fected milk have been reported from England for a 
number of years and, in recent years, several outbreaks 
of the disease, affecting thousands of persons, have oc- 
curred in this country. In some instances the infection 
of the milk was traced to cows affected with streptococcic 
