220 Animal Micrology 



them in a watch-glass with a 1 per cent, aqueous solution of 

 chloretone until they are immobilized and then rapidly transfer- 

 ring them to 5 per cent, formalin. Other fixing agents than 

 formalin can be used. 



DISTOMES 



Perhaps the most easily obtained form is the one which is 

 found in the liver of the cat. Search for it in the bile passages. 

 Fix it in hot corrosive sublimate, wash out with alcohol to which 

 tincture of iodine has been added, and stain for 24 hours in alum 

 cochineal (reagent 27, Appendix B), or hemalum (reagent 47). 

 As with Planaria, they should be compressed between two glass 

 slides (see chap, xiii, iv, A, 7). 



If the large liver fluke of the sheep (Fasciola hepatica) can 

 be obtained, both the alimentary canal and the excretory system 

 may be injected with finely powdered carmine in water. A sepa- 

 rate fluke should be used in each case. For injection, a very fine- 

 pointed cannula with rubber cap is used, or the manipulator may 

 operate the cannula by simply blowing through it. The excretory 

 system is injected through an incision made with a sharp-pointed 

 scalpel in the median line near the hinder end of the animal. For 

 the alimentary canal, the incision should be made about 1 mm. to 

 one side of the median line. When the injection is completed, 

 flatten the animal somewhat between two slides (see chap, xiii, 

 iv, A, 7), harden in 95 per cent, alcohol for 12 to 24 hours, then 

 dehydrate, clear, and mount in balsam. 



CESTODES 



Near large cities an unlimited supply of the sheep tapeworm 

 (Monieza) can usually be secured from slaughter houses. Ample 

 supplies can ordinarily be obtained from dogs, or, less frequently, 

 from cats. Tapeworms can be kept alive for considerable length 

 of time in tepid normal saline. The most instructive portions to 

 mount are scolex, and sexually mature proglottids. For fixing 

 and staining use the same methods as for distomes with the excep- 

 tion that cold instead of hot corrosive sublimate should be used. 

 The scolex should not be compressed. 



