28 THE LIVER-FLUKE. 



alimentary canal of another, with a thin injection, stich as 

 freshly precipitated Prussian blue, suspended in water. 

 Inject the coloured fluid, by means of a very fine glass 

 cannula provided with an indiarubber cap, into the hinder 

 end of the animal ; in the middle line for the excretory system, 

 and about 1 mm. from it for the alimentary canal. Place the 

 animals between glass slips, and tie the slips together with 

 cotton. Put the slips with the animals betiveen them into 

 alcohol (90 per cent.) for twelve hours or more, luhen the speci- 

 mens may be dehydrated, cleared, and mounted in balsam. 



2. Sqiheeze a specimen somewhat more tightly between two 

 glass slides, and leave it in corrosive acetic mixture {see 

 Appendix) for five or six hours. Wash well with 60 per cent., 

 70 per cent., 80 per cent, alcohol for about two days. Pass 

 gradually doiun to water, and stain ivith weak hcemalum for 

 twelve hours. Wash for the same length of titne in 1 per cent, 

 alum solution. Then pass gradtially through water, 50 per 

 cent., 10 per cent., dO per cent., to absolute alcohol {two hours). 

 Clear in cedar-wood oil, and mount in balsam. 



A. External Characters. 



1. In form the animal is flat and oval, with a blunt tri- 



angular projection from its broad anterior end. 

 Its length is about an inch and a half, its breadth 

 about half an inch. 



2. The mouth is an oval aperture at the anterior end, in 



the middle of the cup-shaped anterior sucker. 



3. The ventral sucker is a muscular cup in the mid- ventral 



line, near the junction of the triangular anterior 

 portion with the broader part of the body. 



4. The genital aperture, through which the penis may be 



protruded, is on the ventral surface between the two 

 suckers, and slightly nearer the posterior qne. 



5. The cuticle is a thin layer covering the whole animal. 



Its surface is covered with minute backwardly 

 directed, pointed scales, which are best seen in a 

 specimen kept in spirit and dried at the moment of 

 examination. 



