METHOD OF DESCRIBING CULTURES 63 



fusibility, solubility, influence of acids and 

 alkalis. 



5. Gas-production in glucose media: To be filled 

 out only in case of actual observation. In 

 fermentation-tubes note the growth in either 

 arm or both arms, recognized by turbidity. 

 Note the total percentage of the gas formed in 

 24 and 48 hours. Reaction may be tested by 

 the addition of litmus-solution. Gas formula 



expressed : . 



CO 2 



6. Acid or alkali production in litmus milk. 



7. The production of indol or nitrites, or both, 

 is tested on the sixth day of observation in a 

 culture in Dunham's peptone-solution or 

 sugar-free broth. 



NOTE. Indol is a decomposition product of 

 proteids and belongs to the aromatic series. 

 Nitrites are the result of reduction from nitrates. 

 The ability of organisms to produce these reactions 

 are of great importance in their differentiation. A 

 control test with a tube of sterile medium should 

 always be made. 



8. Enzym-production : Froteolytic enzym-pro- 

 duction noted by the liquefaction of gelatin or 

 casein. Coagulative, by precipitation of casein, 

 if acid-formation is absent, or present only in 

 quantities less than 0.3 per cent. Diastatic, by 

 the digestion of starch (potato). 



9. Characteristic odor. 



10. Pathogenesis : What pathogenic effect has the 

 organism on man ? What effect on animals, 



