244 MICROSCOPIC AND CULTURAL STUDY OF BACTERIA 
tion of oxygen. Wright^ has mamtained anaerobic conditions in test- 
tube cultures with alkahne pyrogallate solution. Test-tubes are 
prepared with absorbent cotton plugs, which are made tighter than 
ordinary usage demands. After the culture medium (freed from dis- 
solved oxygen by heating and rapid cooling) is inoculated, the cotton 
plug is pushed into the tube until the upper end is about 15 mm. 
below the top. The space above the cotton plug is filled loosely with 
dry pyrogallic acid, and a strong solution of sodium hydroxide, 2 to 
3 cc, is added to dissolve the acid. Immediately a tightly fitting 
rubber stopper is inserted into the mouth of the tube. The alkaline 
pyrogallate solution absorbs the oxygen within the tube, leaving an 
atmosphere of nitrogen. 
Fig. 33.— Flask and test-tube for the cultivation of anaerobic bacteria. The flask or 
tube is sterilized with the medium well above the level of the ball. The ball itself is 
sterilized separately, and introduced as soon as the flask or tube has cooled sufficiently 
to inoculate. The ball is then dropped in, and acts as a seal, keeping the oxygen from 
the contents.- 
The addition of bits of fresh, sterile tissue,^ fresh, sterile defibrinated 
blood, or of the coagulum which is formed during the coagulation of 
meat infusion adds greatly to the nutritional value of cultures for the 
growth of anaerobic bacteria. The cooked meat coagulum left over 
from the preparation of meat infusion (see p. 210) added in amounts 
of about 3 to 5 gm. to fermentation tubes makes a very acceptable 
substitute for fresh sterile tissue. 
Special mention of the preparation of tissue media is made in the 
sections on Specific Anaerobic Organisms. 
Mallory and Wright: Pathologic Technic, 4th ed.. p. 126. 
Kendall, Ryan and Cook: Jour. Infec. Dis., 1921, 29, 227. 
Theobald Smith: Centralbl. f. BakterioL, 1890, 7, 502. 
