GENERAL BACTERIOLOGY 99 



2. Transfer 3-5 loopfuls (according to the intensity 

 of the growth, to be judged by the degree of cloudiness) 

 of the broth culture to a sterile tube of Dunham's solu- 

 tion, or sterile physiological salt solution. 



3. Shake well, avoiding air bubbles as much as 

 possible. 



4. Transfer 4 or 5 loopfuls from this suspension to a 

 melted agar tube. 



5. Shake this carefully by rolling the tube between 

 the palms of the hand. 



6. Transfer 4 or 5 loopfuls of this agar tube (2) to 

 the second agar tube (3), and mix as above. 



7. More tubes may be inoculated in the same way, 

 resulting in still higher dilutions if this is desirable. In 

 the meantime the inoculated tubes should be replaced 

 in the water bath, so as to keep them liquid. 



8. Pour the contents of the tubes, one after the 

 other, into sterile petri dishes. 



9. Tip the petri dishes so as to distribute the medium 

 evenly over the bottom. 



10. Label them with the name of the organism and 

 the date. 



11. Set aside on a level place to solidify. 



12. When solidified, place them in the thermostat 

 bottom up, in order to avoid moistening the surface 

 of the agar by the condensation water dropping from 

 the cover. 



NOTE. If the surface were moistened, the colonies would 

 run together and the characteristic appearance be destroyed. 

 Gelatin plates, on the contrary, are placed cover up. Conden- 

 sation water does not form on these plates and gelatin may be 

 liquefied by the organisms. The liquefied part would then fall 

 from the medium on the cover and ruin the plate. 



