ANAEROBIC METHODS 19 
ticine. After this is done air is excluded and the potassium hydroxide 
and pyrogallic acid are mixed by tilting the dish. 
Zinsser’s Method. The main apparatus involved in the applica- 
tion of this method is a set of circular glass dishes similar to a Petri 
dish except that they are much deeper and a larger space is left, between 
the sides. The agar which has been inoculated with the sample is 
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Nae ol 
A SSAA 
ASSSSS Uy; 
C 
Fig. 18.—McLeod’s Anaerobic Culture Apparatus. 
poured into the smaller of the dishes. This is allowed to harden and 
the excess of moisture is evaporated. Into the other dish, is placed 
a quantity of pyrogallol, over which the smaller dish is inverted. So- 
dium hydroxide is poured into the larger dish. While this is reacting 
with pyrogallol, an oil such as abolin is dropped into the same place. 
This successfully seals the chamber which is formed by the two dishes. 
Torrey’s Method. This method was especially successful in the 
hands of Torrey for the isolation of B. bifidus and B. acidophilus. 
er ranting nn nae nanan nocturne ng anirseaanmenenna 
Fig. 19.—Cross-section of Torrey’s Anaerobic Chamber. 
A, Solid Medium Containing the Sample, B, Agar which has been Heavily Inoculated with 
B subtilis or B mesenterrcus, C and D, Petri Dishes which Form the Chamber 
It is similar to the method devised by Zinsser. A Petri dish about 
10 em. in diameter and about 2 cm. high is poured and inoculated with 
the sample under investigation. It is placed in an incubator to remove 
excess moisture and dry the sides of the dish. This is important since 
too much moisture will allow contamination with the culture which is 
used to absorb the oxygen. This dish after drying is inverted into 
another dish, containing agar heavily inoculated with Bacillus cereus, 
of at least 12 cm. in diameter. The agar in the lower plate forms a seal, 
and the strict aerobic organism Bacillus cereus will use up the free 
oxygen. This apparatus is placed in an incubator in a moist chamber 
to prevent evaporation of the agar in the larger dish. 
