PLATE CULTURES 26l 



Reaction of nutrient media. 

 Resistance to lethal agents : 

 Physical : 

 Desiccation. 

 Light. 

 Colours. 



Chemical germicides. 

 Vitality. 

 5. Pathogenicity : 



Susceptible animals, subsequently arranged in 



order of susceptibility. 

 Immune animals. 



Experimental inoculation, symptoms of disease. 

 Post-mortem appearances. 

 Virulence : 



Length of time maintained. 

 Optimum medium? 

 Minimal lethal dose. 



Exaltation and attenuation of virulence? 

 Toxin formation. 



MACROSCOPICAL EXAMINATION OF CULTIVATIONS. 



In describing the naked-eye and low-power appear- 

 ances of the bacterial growth the descriptive terms 

 introduced by Chester (and included in the following 

 scheme) should be employed. 



SOLID MEDIA. 



Plate Cultures. 



Gelatine. Note the presence or absence of lique- 

 faction of the surrounding medium. If liquefaction 

 is present, note shape and character (vide page 269, 

 "stab" cultures). 



A gar. No liquefaction takes place in this medium. 

 The liquid found on the surface of the agar (or at the 

 bottom of the tube in agar tube cultures) is merely 



