CULTURES IN THE FERMENTATION-TUBE, 77 
culture to be studied on the fluid in the bulb with 
a sterile needle. 
(c) In the case of gas formation, at the end of 
every twenty-four hours, for several days, mark the 
level of the fluid in the closed branch upon the 
tube or measure it with a millimeter scale. 
(d@) Record the result in percentages of the length 
Fic. 48.—Bacterium anthracis: colony three days old 
upon a gelatin plate ; adhesive preparation ; x 1000 (Frankel 
and Pfeiffer). 
of the closed branch. If I cm. of gas forms in a 
10 cm. tube, 10 per cent. of gas is said to have 
formed. 
(e) To test the relative amount of carbon dioxid 
and hydrogen present. Fill the bulb completely 
with a 2 per cent. solution of sodium hydroxid. 
Place the thumb over the mouth of the bulb, and 
