20 



A MANUAL OF BACTERIOLOGY 



forceps, rinse it quickly in water and lay the tube with the open 

 end near the center of the drop. Put on the cover glass and 

 examine with the ^- (4 mm.) objective. 



3. Note the subsequent movements of the free-swimming 

 organisms as they enter the area where the bouillon is diffusing 

 from the open end of the tube. Study the reactions which ulti- 

 mately bring them into the tube. How do you explain them ? 



Exercise 25. Arrangement of Bacteria with Respect to Each Other 



1. Make bouillon cultures of the following organisms : Micro- 

 coccus (any species), Sarcina lutea, B. prodigiosus, B. subtilis, 

 Microspira (any species), Spirillum rubrum. 



2. Make stains and hanging-drop preparations after thirty-six 

 hours. 



3. Examine with the oil-immersion objective and classify the 

 organisms in the following table : 



