132 



THE ART OF MAKING MICROSCOPE SLIDES 



T. S. intestine 



elapsed, the sections are transferred to 

 fresh distilled water where they are thor- 

 oughly washed. Each slide is then taken 

 individually and dipped up and down in 

 the phloxine solution until a casual inspec- 

 tion shows the background to be yellow- 

 pink. The intensity of stain for the back- 

 ground, in a case like this, is a matter of 

 choice, some people preferring a faint 

 stain and others a darker stain; it must be 

 remembered, in judging the color, that the 

 section will seem darker after it has been 

 cleared than it does in water. 



As soon as it has been found from a 

 single shde what is the time required to 

 produce the desired degree of staining, the 

 remainder of the slides are placed in the 

 phloxine solution together, left the ap- 

 propriate time, and then transferred to 

 distilled water until no more color comes 

 away. The shdes are then passed from dis- 

 tilled water to 95 % alcohol where they are 

 left for about five minutes, then to fresh 

 95% alcohol, where they are left for five 

 or six minutes before being passed to ab- 

 solute alcohol. The purpose of using the 

 95% alcohol is not to diminish diffusion 

 currents but simply to save diluting the 

 absolute alcohol by passing slides directly 

 from water to it. After the slides have 

 been for two or three minutes in absolute 

 alcohol, a single slide is taken and passed 

 into the absolute alcohol-xylene mix- 

 ture for perhaps two minutes and then 

 passed to xylene. This slide is then ex- 

 amined by reflected hght against a black 

 background and should be as nearly as 

 possible transparent with only a faint 

 opalescence. One of the commonest faults 

 in mounting sections is dehydrating them 

 imperfectly, for if there is any water 

 which has been carried through the proc- 

 ess into the xylene (in which water is solu- 

 ble in the extent of about }i of 1 %) this 

 water will be extracted by the section 

 which is in itself an excellent dehydrating 

 agent. There is a world of difference be- 

 tween a i^erfectly cleared (that is glass- 

 clear) slide and one which is only more or 

 less dehydrated so that it appears faintly 

 cloudy. If the shde does not appear to be 

 sufficiently dehydrated the whole of the 

 remaining slides should be transferred to 



fresh absolute alcohol and another one 

 tried. When it has become apparent from 

 the examination of the test slide that de- 

 hydration is complete, the remaining 

 slides may be run up through absolute 

 alcohol and xylene and accumulated in 

 the final jar of xylene. 



As balsam was discussed in the body of 

 this chapter, we suggest using at the pres- 

 ent time the medium of Kirkpatrick and 

 Lendrun (Chapter 26 M 34.1 Kirkpatrick 

 and Lendrun 1939). Next clean the ap- 

 propriate number of coverslips: in the 

 present instance a %-inch circle would be 

 admirable. The author cleans his cover- 

 slips in the same manner as he cleans his 

 slides: by mping with a weakly acid, alco- 

 hol solution. Each slide is taken individu- 

 ally, drained by its corner, laid on flat 

 surface, and a drop of mounting medium 

 placed on top. The coverslip is then placed 

 on the mounting medium and pressed 

 down with a needle. It should not be 

 pressed absolutely into contact with the 

 shde or too thin a layer of mounting 

 medium will be left; some experience is 

 recjuired to judge when the coverslip has 

 been pushed down far enough. If this is 

 done skillfully the surplus mounting 

 medium will form a neat ring around the 

 outer surface of the cover. If it does not do 

 so, care should at least be taken that no 

 ])ortion of the cover is devoid of surplus 

 mountant which will be sucked under the 

 coverslip as the solvent evaporates. These 

 vslides should be left to dry at room tem- 

 perature for about one day and then 

 placed on a warm plate for about a week. 

 After they are dried the surplus dry 

 mounting medium should be scraped off 

 with a knife and the excess remaining 

 after scraping removed carefully with a 

 rag moistened in 90% alcohol. The shdes 

 are again dried overnight and then should 

 be ringed with some colored varnish using 

 the technique described in Chapter 2. 

 This ring does not assist the preservation 

 of the mounting medium l)ut it has always, 

 in the writer's experience, assured that the 

 sUde when placed in the hands of students 

 will be treated with more respect than a 

 non-ringed slide. The slide, after labeling, 

 is now complete. 



