190 BACTERIOLOGY. 



in doing this, touch the objective or the gelatin, it must- 

 be sterilized at once and the operation repeated. When 

 the end of the wire has been brought over the colony, 

 gradually lower the point till it touches, or cuts the colony 

 into two. 



Now carefully remove the wire, without touching the 

 microscope or some other portion of the gelatin. A tube of 

 solid gelatin is held in the left hand in an almost horizontal 

 position, the plug is then removed by grasping it with the 

 little finger of the right hand (Fig. 29). The mouth of the 

 tube should be flamed in order to remove any adherent cot- 

 ton. The platinum wire, which has a small portion of the 

 colony attached to it, is now slowly forced down the center 

 of the gelatin, to the bottom of the tube. The cotton plug 

 is at once replaced, the wire sterilized and the tube set- 

 aside. 



Transplantation can, of course, be made direct from a 

 colony provided it is very far removed from any adjoining 

 one. A careful microscopic examination should be made of 

 the surrounding gelatin looking out especially for the pres- 

 ence of exceedingly small colonies. 



The stab culture thus made is a pure culture, and should 

 now be labelled with the name of the organism and date, 

 and set aside to develop. In a few days development takes 

 place along the line of inoculation, and, a more or less char- 

 acteristic growth results. 



The manner of growth should be observed daily. Hang- 

 ing-drop and stained preparations can be made, if it is de- 

 sired, from the tube cultures. When the gelatin is very old, 

 and hence too solid, it tends to split as soon as the plat- 

 inum wire is forced into it. This is remedied by melting the 

 gelatin and allowing it to re-solidify. Occasionally, the 

 liquefied gelatin is placed in an inclined position, till it soli- 

 difies. A streak culture can then be made by drawing the wire 

 over the surface. 



