374 Special Procedures II (chap. 23) 



disturb the slides. Leave overnioht. Remove slides and transfer animal 

 to fresh fixative. 



Small trematodes can be shaken in a small amount of 0.5-1.0% salt 

 solution: 3 minutes. Add saturated mercuric chloride plus 2% acetic 

 acid. STiake for several minutes. Change to fresh fixative: 6-12 hours. 

 If they should be flattened, they can be laid on a slide and covered with 

 another slide or, if very delicate, Avith a cover glass. Pipette fixative 

 carefully along the side of the cover and then lower carefully into 

 fixative. 



Cestodes. Place a large tapeworm in ice water until relaxed (over- 

 night). Then flatten between glass plates for microscope-slide whole 

 moimts (as for trematodes — see above). For museum mounts, the worm 

 can be wound on a tall bottle or 100 ml. graduate and fixative poured 

 over it. 



Small cestodes can be stretched from an applicator stick supported 

 over a tall container and fixative poured down the length until they 

 iiang straight. Then immerse them completely. Then they can be 

 flattened between microscope slides. 



Nemertinea. Drop into saturated mercuric chloride-acetic acid 

 (95/5). 



NEMATHELMINTHES. 



Nematodes (hookworms). Shake 3 minutes in physiological saline. 

 Pour off and drop Avorms into hot glycerol alcohol (70-80% alcohol plus 

 10% of glycerol). A sublimate fixative can be used, (also for ascaris) 

 Very small nematodes c an be relaxed and killed in a depression slide 

 or watch glass by gentle heat. An incubator regulated to 50-52 °C is most 

 reliable. If using a flame or hot plate, be careful not to boil the worms. 

 Transfer to fixative. 



Formalin-acetic-alcohol is an excellent fixative for small nematodes: 



95% ethyl alcohol 12-20.0 ml. 



glacial acetic acid 1.0 ml. 



formalin 6.0 ml. 



distilled water 40.0 ml. 



If a few drops of saturated aqueous picric acid is added, the worms take 

 up a little color. 



Slide whole mounts are easy to prepare. Place the Avorms in the al- 

 cohol glycerol mixture in an incubator (35-37 °C) or on top of an oven 

 to permit slow evaporation of the alcohol. When the solution is almost 



