IMPORTANT PATHOGENIC BACTERIA 139 



make cultures and cover-slip preparations from the 

 site of the inoculation. 



9. Special study. Inoculate a white rat with garden 

 earth subcutaneously or in a pocket above the root of 

 the tail. Note the condition of the animal daily. 

 When dead, make cultures and cover-slip preparations 

 from the site of the inoculation. 



SECTION 14 



ISOLATION OF UNKNOWN BACTERIA FROM A 

 MIXTURE 



1. Make hanging-drop, stained, and Gram prepa- 

 rations from the mixture. Note observations and re- 

 sults. 



2. Melt five or six agar tubes, and cool to 43 C. 



3. Transfer 5 or 6 loopfuls of the mixture to a tube 

 of liquid agar, from this to a second, and so on until all 

 the melted tubes are inoculated. 



4. Pour into sterile petri dishes, and mark them 

 with successive numbers and the date. Place in the 

 thermostat at 37 C. 



5. After 24 hours examine the colonies under the 

 low power, describe them in the usual manner, and 

 transfer to agar slants all those which appear different. 



6. Transfer to dextrose agar and litmus milk and 

 incubate at 37 C. for 24 hours. Retain dissimilar 

 cultures and proceed with the usual routine study. 

 Make hanging-drop, stained, and Gram preparations, 

 transfer to all media, describe the culture character- 

 istics, and make sketches. 



7. Special tests may become necessary after 24 or 

 48 hours. Such tests may consist of 



