18 BACTERIOLOGICAL APPARATUS 
placed on its support, introduce the NaOH by means of a pipette into 
the bottom of the tube and seal the tube immediately with a rubber 
stopper. 
Wright’s Method. This is another absorption method and is 
different from the others only in method of procedure. It is especially 
adaptable to the isolation of anaerobic spore-forming bacteria. Decimal 
dilutions of the sample are introduced into sterile litmus milk. About 
1 in. above the meniscus of the milk a tight cotton cylinder is forced 
upon which are put about 2 gms. of pyrogallol. This is treated with 
strong NaOH and the original plug replaced in the tube. This tube 
should then be heated for fifteen minutes at 80° to kill all vegetative 
bacteria. Later incubation will give the characteristic changes. 
Lentz’s Method. This requires a glass plate 125 mm. square and 
cellulose absorbent rings. Before using the rings are soaked in pyrogal- 
lic acid and immediately before the culture is started in 1 per cent 
potassium hydroxide. The plate with the culture is inverted over the 
cellulose ring, being sealed to the glass with plasticine. 
ht 
hh ee 
— 
Fig. 16.—Lentz’s Anaerobic Fig. 17.—Kuster’s Anaerobic 
Apparatus Culture Apparatus. 
Kuster’s Method. This depends upon the same principle as 
McLeod’s and Lentz’s methods. A glass absorption chamber is used 
having a small hole in the top through which is introduced the absorp- 
tion substance. The Petri dish containing the culture is inverted over 
this and sealed with plasticine. 
McLeod’s Method. This method requires a porcelain dish con- 
sisting of two separate chambers for containing the pyrogallic acid and 
potassium hydroxide. The special Petri dish has its free edge turned 
inward and upward. Around the upper cover of the porcelain dish 
is a groove to contain plasticine which prevents the ingress of air. 
About 7 c.c. of a 10 to 20 per cent pyrogallic acid is run into the chamber 
marked A in Fig. 18. Into part B are put 7 c.c. of a 10 per cent potas- 
sium hydroxide. The Petri dish is then pressed down into the plas- 
