PARASITIC ROUNDWORMS 



509 



chamber. The best clearing fluids are synthetic oil of wintergreen 

 (methyl salicylate) and xylol. As stains, Delafield's hematoxylin, 

 Ehrlich's acid hematoxylin, and Mayers' para- 

 carmine give good results. For sections the first 

 two are advised, also a stain made by saturating 

 a one per cent phenol solution with thionin. 

 Special methods were worked out on the nerv- 

 ous system by Goldschmidt. Nematodes may 

 also be studied by staining intra vitam by 

 thionin without phenol and by methylene 

 blue. 



When specimens are to be transferred to bal- 

 sam or damar, it is wise to pierce the body 

 wall with a fine needle. Some skill is necessary 

 to avoid injury to internal organs. When 

 transferring the worms to thin balsam place 

 them in paper cups and allow the medium 

 to dialyze into them. Sections are difficult to 

 make but possible by the use of very hard 

 paraffin and great care in making the transfers. 

 Vacuum embedding is helpful in securing good 

 infiltration. 



For Gordiacea the alcohol-glycerine method 

 is useless; on the whole the corrosive subli- 

 mate-acetic mixture works best, but should be 

 used warmed to 56 or 60 C. In other respects 

 the instructions for nematode technic apply 

 here also. 



The Acanthocephala are best killed and fixed 

 in the corrosive sublimate-acetic mixture and 

 do not come out well in glycerine-alcohol. In general methods 

 used for flatworms work well with these forms also, but for 

 more precise results on any of the roundworms each worker 

 must develop a special technic. (Compare further Looss, 

 Ransom, Magath.) 



The following distinctly artificial key may be used to separate 

 the three classes of Nemathelminthes; it must be supplemented by 



U 



FiG.Sn. Differentiator 

 for dehydrating, a, reser- 

 voir; b, object holders; c, 

 filter and regulation de- 

 vice; d, safety tube; k, 



long, and is shown sec- 

 tioned in the figure. In 

 filling avoid bubbles, e, 

 end piece of differentiator 



alcohols. (After Magath.) 



