Manual of basic techniques for a health laboratory - libdoc.who.int

198 Manual of basic techniques for a health laboratoryFig. 5.1 Making an inoculating loop5.2.3 Preparation of smears1. Flame the loop until it is red-hot: hold the loop just above the blue part of theflame, as close to the vertical as possible (Fig. 5.2). Allow it to cool (count to20).2. Take a portion of the specimen to be examined by placing the loop flat on thesurface of the liquid (Fig. 5.3).3. Number a slide, then press the loop flat on to the centre of the slide (Fig. 5.4).4. Still holding it flat against the slide, move the loop in an oval spiral, outwardsfrom the centre (Fig. 5.5).Leave a space between the specimen and each of the four sides of the slide. Letthe slide dry completely in the air.5. Repeat step 1.Unmarked smears are sometimes received in the laboratory from outside sources.To find out on which side of an unmarked slide the smear has been made, turn theslide so that it reflects the light from the window:●●The side without the smear will shine.The side with the smear will not reflect the light.Fig. 5.2 Flaming an inoculating loopFig. 5.3 Collecting a sample using an inoculatingloopFig. 5.4 Transferring a sample to a slideFig. 5.5 Preparing a smear