THE LIVER-FLUKE (Fasdola or Distoma hepatica) 



The adult Liver-fluke is commonly found in the bile-duets of the sheep. It 

 causes the disease known as " liver rot." 



External Features. 



It is an unsegmented and flattened worm, leaf -like in form and about an 

 inch long. At its broader end it has a triangular projection, the head-lobe or 

 cephahc cone. The surface of the body is devoid of cilia, but is covered by 

 minute spines pointing backwards. At the tip of the head-lobe is the small 

 cup-shaped anterior sucker with the mouth in its centre. On the ventral 

 surface is the ventral sucker, situated just behind the head-lobe. The genital 

 aperture is situated between the anterior and the ventral suckers, but nearer 

 the latter. The excretory pore lies in the middle of the posterior end of the 

 body, slightly on the dorsal surface. 



Alimentary System, 



In order to make out this system clearly, the fluke may be injected through 

 the mouth with a solution of Prussian blue. It should then be placed between 

 two slides, tied together, so as to flatten it. Put the slides with the fluke into 

 90 per cent, alcohol for about twelve hours, and then dehydrate, clear, and 

 mount in balsam. The mouth leads into a small ovoid muscular pharynx. 

 From this a short oesophagus leads to the intestine, which immediately divides 

 into two parts, each giving off a number of blind pouches or caeca. The intestine 

 ends blindly posteriorly, there being no anus. 



Excretory System. 



This may be seen by an injection (similar to that in the case of the alimentary 

 system) made in the middle line of the body near the excretory pore. It consists 

 of a longitudinal main trunk opening at the posterior end by the excretory pore. 

 The trunk is formed from the union of two anterior ducts on each side. The 

 posterior two are dorsal, the anterior two are ventral. These ducts are formed 

 from smaller ducts, and these in turn from numerous capillary tubules, each of 

 which begins with a flame- cell or excretory cell. 



Reproductive System. 



This system is complicated. The animal is hermaphrodite. 



1. Female. 



The ovary is a branched and unpaired organ lying in the anterior part of the 

 body on the right side. A short and narrow oviduct leads from the ovary 

 towards the middle line to join the median yolk-duct or vitellarian duct, which 

 is formed by the union of two transverse ducts leading from the junction of the 

 two long lateral ducts on each side. These are formed from the numerous 



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