330 
Journal of Agricultural Research 
Vol. II, No. 4 
(4) Two classes of streptococci seem to survive Pasteurization: (a) 
Streptococci which have a low majority thermal death point but among 
which a few cells are able to survive the Pasteurizing temperature. This 
ability of a few bacteria to withstand the Pasteurizing temperature may 
be due to certain resistant characteristics peculiar to a few cells or may 
be due to some protective influence in the milk. (6) Streptococci which 
have a high majority thermal death point. When such is the case, the 
bacteria survive because the majority thermal death point is above the 
temperature used in Pasteurization. This ability to resist destruction 
by heating is a permanent characteristic of certain strains of streptococci. 
(5) The thermal death point determinations in this work were made 
in milk in such a manner as to represent actual conditions of Pasteuriza¬ 
tion by the holder process; therefore the results show what may be ex¬ 
pected in commercial Pasteurization, and it is evident that some strep¬ 
tococci may survive the process. However, different results might have 
been obtained if a larger number of cultures had been studied and if other 
methods and media had been used for determining the thermal death 
points. 
