METHODS FOR MICROSCOPIC STUDY OF BACTERIA 235 
of oxygen. This mediuni is simply prepared and suitable for the 
cultivation of practically all anaerobic bacilli. Stock cultures may 
be kept in it for months, because a majority of these organisms sporu- 
late in the medium with considerable readiness. 
V. The Cultivation of Bacteria. — 1. Inoculation of Culture Media.— A 
platinum wire of 24-gau,ue is generally used to transfer bacteria from 
medium to medium. A piece of platinum wu-e^ 3 inches in length 
is fused into the end of a glass rod 5 mm. in diameter and about 15 
cm. in length. Metal handles are preferred by many; they possess 
the great advantage of not breaking, but become heated during the 
process of sterilization. The straight wire or "needle" is commonly 
used for the inoculation of slant and stab cultures in solid media; 
for the inoculation of fluid media a loop is formed on the end of the 
wire. The use of the loop permits of the transfer of a greater amount 
of material. It is occasionally necessary to transfer more material 
than a drop or two obtained with a loop in order to insure growth, 
Fig. 22.— Needle sterilizer. (A. de Khotinsky.) 
and for this purpose sterile capillary pipettes are very convenient. 
Many anaerobic bacteria and organisms which grow poorly in artificial 
media must be transferred with the pipette. 
The transfer of bacteria from media to media involves the following 
steps : 
(a) Flame cotton plugs to destroy moulds and spores of bacteria; 
extinguish flame. 
(6) Twist cotton plugs to destroy adhesion to the neck of the 
tube. The plugs may then be removed intact. 
(c) Sterilize platinum wire in Bunsen flame. Heat wire white hot 
and pass that portion of the handle adjoining the wire through the 
flame, rotating it between the fingers while doing so. Allow the 
wire to cool. 
(r/) Grasp the tubes in the left hand and remove plugs from the 
tubes, holding one between the third and fourth fingers of the right 
> A cheap and efficient substitute for platinum wire is "Nichromc" wire. It is rather 
less durable than platinum, and melts at a lower temperature. 
