22O Cultures, and their Study 



tion on the plate, is brought to the center of the field and the 

 plate firmly held in position with the left hand. A sterile 

 platinum wire is held in the right hand, the little finger, com- 

 fortably fixed upon the stage of the microscope, being used to 

 support the hand. As the operator looks into the micro- 

 scope the point of the platinum wire is carefully brought 

 into the field of vision without touching either the lens of 

 the microscope or any part of the plate beneath. Of course, 

 the wire and the colony cannot be simultaneously looked 

 upon. When the colony is distinctly seen the platinum 

 wire appears as a shadow, but the endeavor should be to 

 make the end of the shadow which corresponds to the point 

 of the wire appear exactly over the colony. It is then 

 gradually depressed until it touches the colony and can be 

 seen to break up and remove some of its substance; or 

 should the colony be tough and coherent, to tear it away 

 from the culture medium. It requires almost as much 

 skill to withdraw the wire from the colony without touching 

 anything as to successfully approach the colony in the first 

 place. The bacterial mass adhering to the wire is now 

 spread upon the surface of agar-agar or stabbed in gelatin 

 or stirred in fluid medium, as the case may be. The 

 higher the magnification under which this operation is 

 done, the more difficult it is. Therefore only low-power 

 lenses should be employed. The transplantation should be 

 made immediately after the wire has touched the colony, 

 the wire not being permitted in the meantime to come into 

 contact with any other object. Immediately after receiving 

 the inoculation, the tube containing the culture medium, 

 held in the left hand, should be passed with a twisting 

 motion through the flame of a Bunsen burner, so that its 

 mouth and the cotton plug shall be heated. The cotton 

 plug of course takes fire, but by vigorously blowing once or 

 twice the fire can be extinguished. The cotton is then re- 

 moved with a twisting motion of the plug and placed 

 between two fingers of the left hand in such a manner that 

 only the extra-tubular portion of the cotton is touched by 

 the fingers. During the time that the plug is being with- 

 drawn the tube should be held as nearly as possible in a 

 horizontal position, in order that nothing may fall into it 

 from the atmosphere. The inoculation having been made, 

 the plug is returned and the platinum wire heated to redness 

 in order that any remaining bacteria may be killed by the 

 heat. 



