2O2 Cultures, and their Study , 



pocket, the position of the platinum wire is reversed in the glass tub- 

 ing and protected by it. 



Immediately before and immediately after use, the platinum wire is 

 to be sterilized by heating to incandescence in a flame, in order that it 

 convey nothing undesirable into the culture, and in order that it 

 scatter no micro-organisms about the laboratory. 



Fig. 47. Platinum needles for transferring bacteria; made from No. 27 platinum 

 wire inserted in glass rods. 



Capillary glass tubes are employed by the French for many of the 

 manipulations. They are made of M- or %-inch glass tubing cut 

 into 25 cm. lengths, heated at the center, and drawn out to capillary 

 ends about 5 cm. long. They are sealed at one end and plugged with 

 cotton at the other, and a number of them, prepared at the same time, 

 sterilized. They can be used for all the purposes for which the 



Fig. 48. Ravenel's platinum wires for bacteriologic use. 



platinum wire is employed, and in addition can be used as con- 

 tainers for small quantities of fluids sealed in them. When about to 

 use such a tube, its sealed capillary end should be broken off with 

 forceps, and the tube sterilized by flaming. 



Technic of Culture Manipulation. Containers of stored culture- 

 media should be kept in an upright position, that the cotton stoppers 



Fig. 49. Capillary glass tubes, a, Pipette for ordinary manipulations; b, 

 constricted pipette in which small quantities of cultures, etc., can be sealed by 

 fusing the glass; c bulbous pipette in which larger quantities of fluids may be 

 sealed. 



are not moistened or soiled. If moistened with the culture-media, 

 molds whose spores fall upon the surface of the stoppers may grad- 

 ually work their mycelial threads between the fibers until they ap- 

 pear upon their inner surface and drop newly formed spores into the 

 contained media. 



In handling tubes care must be taken to stand them up in turn- 



