23 



next to it place tube 3. Remove the cotton plugs and 

 place in their respective places as before. With the ster- 

 ilized cool platinum wire make three successive transfers 

 of gelatin from tube 2 to tube 3. Return the cotton 

 plugs to their tubes, sterilize the wire, and set the tubes 

 aside in the tumbler. 



Each of the three gelatin tubes has now been inocu- 

 lated. Tube 1 usually has a very large number of bac- 

 teria, while tube 2 has less and tube 3 should have but a 

 small number, so that subsequently when colonies develop 

 these should be separated from one another by an appre- 

 ciable distance. It is necessary therefore, to take a very 

 minute amount of material for the inoculation of tube 1 

 in order to obtain good dilutions. In transferring gelatin 

 from one tube to another care must be taken to prevent 

 the wire from coming in contact with the neck or walls of 

 the tubes. 



Prepare the ice plating apparatus for use and then 

 level it. Remove a sterilized glass plate from the iron 

 box by grasping the edges with two fingers ; place it upon 

 the ground plate of the ice apparatus and cover with the 

 bell jar. As soon as the plate is cool it is ready to receive 

 the gelatin. Before pouring the contents of the tubes 

 upon the plates it is necessary, as a matter of precaution, 

 to sterilize the neckof the tube. To accomplish this, cut 

 off the cotton which projects from the tube, push in the 

 plug a trifle, and then rotate the neck of the tube in a 

 flame till the cotton begins to turn yellow. As soon as 

 the neck oi the tube cools the gelatin can be poured. To 

 do this remove the cotton plug with a pair of forceps, ster- 

 ilized in the flame, and place it between the fingers of the 

 left hand. Transfer the tube to the right hand, raise the 

 bell jar somewhat and pour the gelatin onto the centre of 

 the plate. With the lip of the tube spread out the gela- 

 tin as rapidly and as fully as possible, avoiding, however, 

 the edges of the plate. Allow the gelatin to solidify 

 under cover of the bell-jar. 



