BIOCHEMIC CHARACTERS. 179 



by the liquefaction of gelatin, casein, or blood-serum ? 

 Note whether this function is manifested in alkaline or 

 in acid condition of the medium. Does it manifest a 

 precipitating effect (rennet ferment?) upon casein? 

 Note whether this is manifested in alkaline or in acid 

 condition of the medium. Does the organism have the 

 property of breaking up any of the carbohydrates into 

 simpler compounds ? Is this alteration accompanied or 

 not by the liberation of gas ? If so, ascertain the rela- 

 tive amount of gas formed from a given quantity of 

 carbohydrate. Analyze the gas formed, and state the 

 relative proportion of carbon dioxide and residual (ex- 

 plosive) gas formed. If the carbohydrates are broken 

 up without the evolution of gas, then ascertain what 

 intermediary and end-products are formed. Are acids, 

 aldehyde, or alcohol formed? Ascertain the nature 

 of the acids produced. If lactic acid is formed 

 from lactose, ascertain its character by means of the 

 polariscope. 



Ascertain whether the organism produces indol, 

 phenol, or skatol. Are these substances formed with 

 the simultaneous reduction of nitrates to nitrites ? Are 

 the nitrites reduced further into ammonia ? 



Pathogenic Properties. Ascertain whether any of the 

 animals used for experimental purposes are susceptible 

 when inoculated with the organism. Are all species of 

 laboratory animals equally susceptible, or are some 

 immune ? Note the size of the dose and the manner 

 of inoculation that gives the most constant and charac- 

 teristic results. What are the symptoms and post- 

 mortem appearances produced ? What is the location 

 of the organisms in the body of the dead animal ? Are 

 they confined to the seat of inoculation (toxaemia), or are 



