112 



LABORATORY EXERCISES IX BACTERIOLOGY. 



FIG. 34. A, STROKE 

 CULTURE. B. 

 PUNCTURE CUL- 

 TURE. 



As soon as the inoculation is accomplished the needle is to be withdrawn carefully 

 from the tube and flamed before being laid down; if it be wet from some liquid medium 

 with which it has been brought in contact, it should be held for 

 a moment by the side of the flame in order to dry before being 

 thrust directly into the flame, as the bubbles bursting in the 

 flame might scatter the infection and cause harm. The needle 

 having been disposed of, the mouths of the two tubes are held 

 for a moment in the flame to destroy any infection which may 

 be adherent to the lip and might be forced into the interior in 

 the application of the stoppers; and the stoppers are taken up 

 one after the other with a pair of forceps, flamed, and thrust 

 into the tubes. (Do not mix the stoppers.) The newly inocu- 

 lated tube is then properly marked and set aside for develop- 

 ment. 



The manipulation in using the platinum needle is practi- 

 cally the same as the above from whatever source the infectious 

 material is to be obtained or whether the inoculation is to be 

 made upon media in tubes, dishes, on plates, or in flasks. The 

 needle is first sterilized, then brought in contact with the infec- 

 tion, carried into contact with the fresh medium, and either 



drawn over its surface in a stroke or a smear or thrust into the mass as a stab (or 

 agitated in liquid media), withdrawn from the medium, and flamed; the lip of the 

 tube or flask flamed; the stopper flamed and readjusted (or 

 the cover of the dish reapplied). 



Swabs. Sterile cotton swabs are often convenient for ob- 

 taining the infectious matter for inoculation, as from diph- 

 theritic sore throats or the surface of a wound. Usually a 

 number of such sterile swabs are kept ready in laboratories, 

 inclosed in sterilized test-tubes. The tubes should be at least 

 seven inches in length and preferably three-fourths of an inch 

 in diameter, A piece of ordinary brass or iron wire is cut a 

 little shorter than the tube and one end is roughened with a 

 file. About this end a firm swab of absorbent cotton is twisted, 

 and its surfaces rolled smooth between the fingers. The oppo- 

 site end is set into a small cork and absorbent cotton is firmly 

 wrapped about it, completely covering in the cork, until the 

 mass will fit closely, but not tightly, in the tube. The tube 

 having been cleaned in the usual manner, the swab is intro- 

 duced into its interior, the cotton plug wrapped about the 

 handle of the wire serving as a stopper for the tube. The whole 

 appliance is now thoroughly sterilized in the autoclave and 

 thereafter a rubber cap is applied over the mouth of the tube 

 to protect against microbic penetration and to keep the swab 

 moderately moist. The tube with the contained swab may be 

 carried to the bedside, where the swab is withdrawn, brushed 

 over the infected surface, and at once replaced in the tube and 

 carried to the laboratory. Here the swab is used just as an 



inoculated platinum needle would be used for the making of smear inoculations upon 

 the surface of media in tubes or dishes or on plates. After the inoculation has been 



FIG. 35. STERILE 

 COTTON SWAB IN 

 TUBE, WITH RUB- 

 BER CAP OVER 

 MOUTH OF LAT- 

 TER FOR GREATER 

 PROTECTION OF 

 SWAB AND TO 

 PREVENT DRYING. 



