242 
MICROSCOPIC AND CULTURAL STUDY OF BACTERIA 
is ready to close up. When the jar is opened, the phosphorus that is 
unconsumed must be placed in water at once to prevent its burning 
when exposed to the air. 
Stock cultures of anaerobes may be kept under strict anaerobic con- 
ditions almost indefinitely provided the cover of the jar fits tightly. 
Mcintosh and Fildes^ have made use of palladium as a catalyst to 
remove oxygen from a proper receptacle, to which hydrogen is admitted 
from a suitable generator. The reaction 
usually starts promptly and good anaerobic 
conditions are soon attained. Several ex- 
plosions have been reported however which 
suggest that this method is not without 
some hazards. 
Wright- has devised a very simple method 
for cultures of anaerobic bacteria in fluid 
media. The process is clearly shown in the 
accompanying two illustrations (Fig. 28). 
Pure cultures of anaerobic bacteria may 
be obtained in an atmosphere of hydrogen; 
plates prepared in the usual manner are 
placed on a rack in a Novy jar or other 
similar vessel provided with a tightly fitting 
stop-cock, through which hydrogen can be 
admitted in sufficient volume to displace 
the air. The stop-cock must be hydrogen- 
tight. The procedure is to place inocu- 
lated plates without covers on a rack 
within the jar in an inverted position, 
one above the other. A few grams of 
pyrogallic acid are placed on the bottom 
of the jar with a small piece of solid sodium 
hydroxide. At the last moment, when 
everything is in readiness, 20 to 30 cc. 
of water are gently poured down the side 
of the jar to prevent spattering, and the 
cover quickly clamped down. A current 
of hydrogen gas, either from a cylinder or 
from a Kipp generator, is passed through 
the jar at a fairly rapid rate. The hydro- 
gen should enter at the top, and the outlet for the gas should be as 
near the bottom of the apparatus as possible. A sample of the 
escaping gas, collected in a test-tube by downward displacement, 
will ignite without an explosion when all oxygen is displaced. The 
inlet tubes are closed, and incubation practised in the usual manner. 
An atmosphere of nitrogen is to be preferred to an atmosphere of 
hydrogen whenever it is practicable. 
1 Lancet, 1916, i, 768. 2 Centralbl. f. Bakteriol., 1900, 27, 74. 
Fig. 28.— Weight's method of 
making anaerobic cultures in 
fluid media. (Mallory and 
Wright.) 
