CULTIVATION WITHOUT OXYGEN. 185 



acid and two parts by volume of an explosive gas consist- 

 ing largely of hydrogen. For determining the nature and 

 quantitative relations of these gases Smith 1 recommends 

 the following procedure : " The bulb is completely filled 

 with a 2 per cent, solution of sodium hydroxide (NaOH) 

 and closed tightly with the thumb. The fluid is shaken 

 thoroughly with the gas and allowed to flow back and 

 forth from bulb to closed branch and the reverse several 

 times to insure intimate contact of the CO 2 with the 

 alkali. Lastly, before removing the thumb all the gas is 

 allowed to collect in the closed branch, so that none may 

 escape when the thumb is removed. If CO 2 be present 

 a partial vacuum in the closed branch causes the fluid to 

 rise suddenly when the thumb is removed. After 

 allowing the layer of foam to subside somewhat the 

 space occupied by gas is again measured, and the dif- 

 ference between this amount and that measured before 

 shaking with the sodium hydroxide solution gives the 

 proportion of CO 2 absorbed. The explosive character 

 of the residue is determined as follows : The cotton plug 

 is replaced and the gas from the closed branch is allowed 

 to flow into the bulb and mix with the air there present. 

 The plug is then removed and a lighted match inserted 

 into the mouth of the bulb. The intensity of the ex- 

 plosion varies with the amount of air present in the 

 bulb." 



CULTIVATION WITHOUT OXYGEN. As we have 

 already learned, there is a group of organisms to which 

 the name " anaerobic organisms " has been given, which 

 are characterized by their inability to grow in the pres- 

 ence of oxygen. For the cultivation of the members of 



i Loc. cit., p. 196. 



