192 Specific Examples of Slide Making 



there until it has turned a bronzy brown on the outside. This appearance 

 can best be detected in reflected light, just as soon as the first bronze 

 sheen appears on the outside of the worm it must be removed to fresh 

 distilled water, where it can remain until all the other worms in the batch 

 have been treated similarly. It will be necessary to renew the potassium 

 permanganate from time to time, which is done by adding a few more 

 drops of the stock solution to the beaker. The strength of the oxalic acid 

 used to bleach the worm is quite immaterial; 2 or 3 per cent, arrived at by 

 guesswork rather than by weighing, is an adequate solution. Since the 

 bleaching of the surface is not nearly so critical as is the deposition of the 

 potassium permanganate, all the worms may be bleached at the same 

 time by pouring off the distilled water and substituting the oxalic acid 

 for it in the beaker. One or two twists of the wrist to rotate the worms in 

 the beaker will result in their turning from a bronze sheen to a dead white. 

 The oxalic acid is poured off without any waste of time, and the worms 

 are washed in running tap water for an hour or so before being dehy- 

 drated in the ordinary way, cleared, and mounted in balsam. Little 

 trouble will be experienced with curling of the worms if they have been 

 fixed and treated as described. If they should curl, they should undergo 

 the final dehydration in 96 per cent alcohol while being pressed loosely 

 between two sheets of glass, which will be sufficient to hold them flat. 



SUMMARY 



1. Anesthetize flukes in warm saline solution with menthol. 



2. Place a layer of filter paper saturated with Gilson's fluid on a glass 

 plate. Have ready another sheet of fixative-saturated paper and another 

 glass plate. 



3. Lay worms about 1 in. apart on paper on glass, cover with second 

 sheet saturated with fixative, lay second glass on top, and add sufficient 

 weight to flatten but not squash worms. 



4. After about 12 hr remove flattened worms to jar of fixative. Fix 1 to 

 6 days. Wash in running water overnight. 



5. Transfer to 1 part Mayer's carmalum diluted with 100 parts 5% potas- 

 sium alum. Leave until internal structures are stained clearly (1 to 3 

 weeks ) . 



6. Wash in 5% potassium alum. 



7. Bleach surface with permanganate-oxalic acid. 



8. Wash thoroughly, dehydrate, clear, and mount. 



