July is, 1914 
Pasteurization of Streptococci 
325 
68.3° C. (155 0 F.) 9 cultures, or 50 per cent, survived. At 71.i° C. 
(160 0 F.) 2 cultures, or 11.11 per cent, survived, but all were destroyed at 
73.9° C. (165° F.). 
From these results, which are shown diagrammatically in figure 2, it 
is evident that the streptococci from the udder are, as a rule, less resistant 
to heat than those from the other sources. Those from the mouth and 
from the feces have about the same resistance, while streptococci from 
milk and cream were very much more heat resistant than those from 
other sources. See Table II. 
Table; II .—Effect of heat on streptococci—cultures classified according to source 
Cultures surviving after heating for 30 minutes at— 
Source. 
48.9* c. 
SiVC. 
54 - 5 * C. 
57 - 3 * C. 
6o*C. 
(l 30 * E.). 
(ms’FA 
(130 9 E.). 
(*35 * E.). 
(i 4 o a E.). 
Feces.. 
/Number. 
45 
45 
45 
44 
31 
100 
100 
100 
97-77 
68.88 
Udder.. 
/Number.. 
.\Per cent.. 
40 
100 
40 
100 
40 
100 
34 
60 
18 
45 
Mouth. 
/Number.. 
36 
36 
35 
3i 
39 
100 
100 
97*33 
88.88 
6l. II 
Milk and cream.... 
/Number.. 
.\Per cent.. 
18 
100 
18 
100 
18 
100 
iS 
100 
18 
100 
Cultures surviving after heating for 30 minutes at— 
Source. 
63.8* C. 
6s.6* c. 
68-3*0. 
7r.i*C. 
73 - 9 * 0 . 
Ci45*F.). 
(150* E.). 
(155* R-). 
(i6o“ F.). 
(i6 S * F.). 
Feces. 
/Number.. 
9 
3 
0 
0 
0 
30 
4-44 
0 
0 
0 
Udder. 
/Number.. 
Hi 
0 
4 
10 
3 
5 
1 
3. so 
0 
0 
Mouth., 
/Number.. 
13 
36. 11 
7 
19*44 
3 
5* 55 
0 
0 
0 
0 
Milk and cream.... 
/Number.. 
17 
94-44 
13 
73. 33 
9 
50 
3 
11.11 
0 
0 
3. THE THERMAL DEATH POINT OE THE TYPICAL AND ATYPICAL CULTURES 
The writers do not consider the chain formation a proper basis on 
which to divide streptococci into typical and atypical groups. How¬ 
ever, grouping is made on this basis in some board-of-health laboratories, 
and some investigators consider that chain-forming streptococci are asso¬ 
ciated with infected udders. For this reason the writers believe it of 
interest to consider the heat resistance of streptococci grouped as typical 
and atypical on the basis of chain formation. 
Among the 139 cultures used in these experiments 22 formed long 
chains, and were for the purpose of this paper considered typical. The 
other 117 cultures formed chains of 10 or less, and were considered 
