CHAPTER VIII 



METHODS USED IN THE CULTIVATION OF BACTEEIA 



INOCULATION OF MEDIA 



THE transference of bacteria from pathological material to media, 

 or from medium to medium, for purposes of cultivation, is usually 

 accomplished by means of a platinum wire or loop. The platinum 

 wire used should be thin and yet possess a certain amount of stiff- 

 ness and be about two to three inches in length. This is fused into 

 the end of a glass rod six to eight inches long. It is an advantage, 

 though not necessary, to use rods of so-called "sealing-in" glass 

 which, having the same coefficient of expansion as platinum, does 

 not crack during sterilization. For work with fluid media, the wire 

 should be bent at its free end so as to form a small loop which 

 will pick up a drop of the liquid. For the inoculation of solid media 

 and the making of stab cultures, a straight "needle" or wire should 

 be used. Other shapes of these wires and spatulae from heavy wire 

 have been devised for various purposes and are easily improvised 

 as occasion demands. 



When making a transfer from one test tube to another, the tubes 

 should be held between the thumb and first and second fingers of 

 the left hand. (See Fig. 12.) The plugs are then removed by 

 grasping them between the small and ring fingers and ring and 

 middle fingers of the right hand, first loosening any possible adhe- 

 sions between glass and plugs by a slight twisting motion. The 

 platinum wire is held meanwhile by the thumb and index fingers 

 of the right hand in the manner of a pen. The wire is heated red 

 hot in a Bunsen flame, and is then passed into the culture tube 

 without being allowed to touch the glass. It is held suspended 

 within the tube for a few seconds to permit of cooling before touch- 

 ing the bacterial growth. The wire is then allowed to touch lightly 

 the surface of the growth and a small amount is picked up. 

 It is then removed from the tube without allowing it lo 



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