On Certain Bacteria from the Air of Nexo York City. 345 



Rosolic acid broth. Useful for decolorization eftects. The 

 deepening of the tint is of little value. 



Pepton and salt broth. For the formation of indol. The test 

 may be applied by adding a few drops of sulphuric acid, and then 

 a verj^ dilute sodium nitrite. Care should be exercised not to add 

 too much. This test is open to the same objection as is the ni- 

 trate test, and in greater degree, in that the characters to be ob- 

 tained from it are not sharp ones. 



BACTERIOLOGICAL DIAGNOSIS. 



Species which will groic on the oridinary media, in presence of air at 20° C. 

 :Micrococci. 



The gelatin is not liqnefied page 345 



The gelatin is ultimately licxuefied page 348 



Bacilli. 



No gas formed in the fermentation tiibe. 



The gelatin is not liqnefied page 355 



Tlie gelatin is ultimately liquefied jjage 364 



Gas is formed in the fermentation tube page 375 



Spirilla (not found in the air). 

 Species which are anaerofiic, rriU not grow on the ordinary media, or require a 

 higher temperature than 20° C. {not investigated). 



NON-LIQUEFYING MICROCOCCI. 



(Synopsis of species). 



Lactose-litmus gelatin reddened. 

 Chromogenic. 



Yellow ; nitrate strongly reduced 1 



Red ; nitrate very slightly reduced 2 



Not chromogenic. 

 ]Milk coagulated. 



Nitrate slightly reduced ; milk coagulated 3 



Nitrate not reduced 4 



i\Iilk not coagulated. 



Growth on agar opaque white 5 



Growtli on agar thin, transparent, poor 6 



Lactose-litmus gelatin made blue. 



Nitrate not reduced ; milk not coagulated. 



Rosolic acid faded 7 



Rosolic acid not changed 



Chromogenic ; orange 8 



Not chromogenic : white 9 



Nitrate reduced ; milk not coagulated. 



Not chomogenic ; Avhite 10 



Chromogenic ; red 11 



