202 



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 J4- 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 



^» 



rig. 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; h, 

 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 mycehal threads between the fibers until they ap- 

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

 contained media. 



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



