135] UFE HISTORY OP GORDIUS AND PARAGORDIUS— MAY 15 



In all cases the sections were fixed to the slide by means of Meyer's 

 albumen fixative. Slides containing older specimens had further to be 

 treated with a very thin solution of celloiden while transferring from abso- 

 lute alcohol to 95% before staining. 



In sectioning adults the friction between the specimen and the knife 

 often caused the ribbon to become highly charged with static electricity. 

 This was especially true of specimens that had become excessively hardened 

 in the process of dehydration and infiltration. The only remedy was to 

 trim the block less closely and make sure that it was properly treated with 

 soft parafl&n. The same rules had to be followed in sectioning crickets 

 and grasshoppers. 



The best stain was found to be iron hematoxylin. Unna's polychro- 

 matic methylene blue method with orcein as a counter stain gave fair 

 results, Mallory's connective tissue stain was useful for demonstrating 

 basement membranes; Delafield's hematoxylin, Ehrlich's hematoxylin and 

 the carmine stains gave very mediocre results. 



The iron hematoxylin method had to be modified according to the 

 developmental stage and condition of the material, and the structures to 

 be shown. For mordanting a 4% solution of iron ammonia alum was 

 used and for staining a 0.5% solution of hematoxylin in water. Sections 

 were usually mordanted about twice as long as they were stained except in 

 case of very short staining periods when they were mordanted about half 

 an hour. 



Older parasitic stages were usually stained from half an hour to one 

 hour, adults from one to two hours or for nerve structures from six to 

 twelve hours, younger stages for very short periods, sometimes not more 

 than thirty seconds. Destaining was nearly always done in a saturated 

 solution of picric acid in water. This was found to take the stain out more 

 uniformly than did the iron alum. 



For counterstaining the slides were left for from twelve to twenty-four 

 hours in xylene to every fifty cubic centimeters of which had been added 

 three to five drops of a saturated solution of eosin in absolute alcohol. 

 Fresh eosin must be added from time to time as it precipitate very rapidly 

 unless there is a large amount of alcohol in the xylene. 



