1889-90.] Dr Griffiths on Researches on Micro-Organisms. 263 
IV. Action of Freezing Mixtures upon certain Micro-organisms. 
Daring these researches, I found that certain micro-organisms 
were killed at low temperatures. 
Tube cultivations of the following microbes were used in these 
experiments : — 
(1) Bacillus tuberculosis. 
(2) Bacterium allii. 
(3) Bacillus subtilis. 
(4) Spirillum tyrogenum. 
The temperatures employed were obtained by using the following 
freezing mixtures : — 
Mixture. 
In the Proportion 
Minimum Tempera- 
of (by weight). 
tures recorded. 
/ Ice, 
\ Salt, 
2 
1 
| - 18° C. 
/ Water, 
\ Ammonium nitrate, 
1 
1 
| - 15° C. 
/ Sodium sulphate, . 
8 
| - 17° C. 
\ Hydrochloric acid, 
5 
After the micro-organisms had been exposed to the above tem- 
peratures for several days, a number of tubes containing sterilised 
agar-agar, blood serum, &c., were inoculated from the contents of 
the above tubes ( i.e ., the tubes exposed to the low temperatures). 
From these experiments the following results were obtained: — 
oo 
rH 
4-3 
3 C. 
At -17° 
C. 
At - 15 c 
’ C. 
For 
1 
day. 
For 
3 
days. 
For 
14 
days. 
For 
1 
day. 
For 
3 
days. 
For 
14 
days. 
For 
1 
day. 
For 
3 
days. 
For 
14 
days. 
Bacillus tuberculosis, 
L* 
D 
D 
L 
D 
D 
L 
D 
D 
Bacterium allii, 
D* 
D 
D 
D 
D 
D 
L 
L 
D 
Bacillus subtilis, 
L 
D 
D 
L 
L 
D 
L 
L 
D 
Spirillum tyrogenum, 
L 
D 
D 
L 
L 
D 
L 
L 
D 
* L = living. D = dead, 
