104 GUIDE TO THE STUDY 



size. The mucosa should be scraped into water and specimens 

 sought with the aid of a microscope. The method of isolating 

 adult trichinae may be used to advantage, particularly if the 

 water is near 38°C. 



Killing and Fixation. — Trematodes may best be fixed in con- 

 centrated aqueous solution of corrosive sublimate plus 2 per cent 

 of glacial acetic acid, or in picro-formol. Under field conditions 

 it is often necessary to drop the specimens into 5 per cent formalin 

 or into 70 per cent alcohol. If the latter is used, specimens may 

 subsequently be softened by soaking in water. 



For small species Looss' shaking method is the most generally 

 useful. The specimens are put in a small vial nearly filled with 

 physiological salt solution and are shaken violently for 3 minutes. 

 One-half of the salt solution is then quickly poured off and 

 replaced by an equal amount of the acetic-sublimate solution and 

 the shaking continued for a minute or so. Then replace with 

 acetic-sublimate solution and fix for 15 to 30 minutes, or up to 

 several hours if desired. Wash in 50 per cent alcohol, for 15 to 

 30 minutes, then in 70 per cent plus sufficient iodine to give it 

 a bright straw color. If the fluid is bleached, change or add more 

 iodine. Too much iodine will injure the staining quality. It is 

 desirable to leave in the iodized alcohol for an hour or more, 

 before washing in clear 70 per cent and storing or staining. 



Often specimens are advantageously killed under light pressure 

 under the cover glass or between two slides held together by 

 rubber bands or thread, while running the fixing agent under. 

 The slide or cover should be lifted occasionally to insure access of 

 the fluid to all parts. Too much pressure will dislocate organs. 

 Miihling kills muscular forms in an extended condition by placing 

 the specimen on a cover glass, cleaning off attached mucus, then 

 quickly pressing over it a hot slide which has been wet with the 

 fixing fluid. Fresh fluid is gradually added from the side, the 

 cover being lifted from time to time. 



Staining and Mounting. — Specimens may be stained overnight 

 in very dilute Delafield's hematoxylin or in borax-carmine. If 

 in the former they should first be washed in water, but if borax- 

 carmine is used they should be transferred from 70 per cent alco- 

 hol. After staining wash in water and differentiate carefully in 

 70 per cent alcohol plus 2 per cent HC1, dehydrate in 80 per cent 

 and 95 per cent for 15 to 30 minutes each, clear in carbol-xylol, 

 and mount in balsam. 



