ATMOSPHERE 



2 95 



11. Connect up the culture flask with the horizontal 

 arm of the gas receiver. 



1 2 . Remove the screw clamp from the rubber tubing, 

 adjust the three-way tap, seal all joints with melted 

 wax, and incubate. 



13. Complete the investigation as described for the 

 previous method. 



BY PHYSICAL METHODS. 



Examine cultivations of the organism with reference 

 to its growth and development under the following 

 headings : 

 Atmosphere : 



(a) In the presence of oxygen. 



(b) In the absence of oxygen. 



(c) In the presence of gases other than oxygen. 

 Temperature : 



(a) Range. 



(b) Optimum. 



(c) Thermal death-point: 

 Moist: Vegetative forms. 



Spores. 

 Dry: Vegetative forms. 



Spores. 



Reaction of medium. 

 Resistance to lethal agents: 



(a) Desiccation. 



(b) Light: Diffuse. 



Direct. 

 Primary colours. 



(c) Heat. 



(d) Chemical antiseptics and disinfectants. 

 Vitality in artificial cultures. 



I. Atmosphere. The question as to whether the 

 organism under observation is (a) an obligate aerobe, 

 (b) a facultative anaerobe", or (c) an obligate anaerobe 

 is roughly decided by the appearance of cultivations 



