PLATYHELMINTHES 165 



is accomplished by the extending forward of the parasite's anterior 

 end, with alternate fixing of the oral and ventral sucker. The majority 

 remain in the bile ducts, though some upon reaching the smaller ducts 

 break through and pass into the liver tissue where they may excavate 

 and destroy large areas. Such migrations may extend through Glisson's 

 capsule to the serous covering of the organ and thus give rise to per- 

 itonitis in addition to the inflammation of the hepatic parenchyma. 

 They do not essentially remain confined to the liver, but may pass 

 through the capsule and serosa into the peritoneal cavity. Others may 

 reach the ramification of the portal vein and set up an endophlebitis 

 with accompanying thrombosis and embolism ; or the hepatic veins may 

 be involved and some flukes be carried by the blood current to the 

 thoracic organs. 



The destruction of liver tissue in hepatic fascioliasis is largely the 

 result of direct irritation due to the spiny processes covering the par- 

 asites. During the first few weeks after being taken up by the host the 

 flukes are small and do not cause a serious irritation. Later they set 

 up an acute inflammatory condition of the bile ducts and liver tissue, 

 the hepatitis remaining more or less localized or becoming generalized 

 according to the number of parasites present and the extent of their 

 migrations. In certain cases there is abscess formation, or hemorrhages 

 may occur due to the breaking down of the walls of blood vessels. The 

 inflammation nmning a chronic course is associated with connective 

 tissue proliferation, causing a thickening of the walls of the ducts. Later 

 this process extends to the interlobular connective tissue and brings 

 about cirrhosis of the liver. 



Flukes which have remained in the bile ducts pass back into the 

 duodenum soon after the reproductive function has been accomplished. 

 It is thought by certain investigators that the period of time which 

 they remain in the ducts does not exceed nine to twelve months. Within 

 the intestines they are much altered by the intestinal juices and pass 

 from the host with the excrement. 



Fascioliasis of Sheep 



S3rmptoms and Course. — An animal harboring but few flukes will 

 give no evidence of fimctional disturbance. This can be readily dem- 

 onstrated in sheep-slaughtering establishments where moderately in- 

 fested livers have been repeatedly found in sheep in prime condition. 

 In heavier infestations a developing period of about three to six weeks 

 intervenes between the taking up of the flukes and the appearance of 

 symptoms. 



In sheep usually the first symptom to be noticed is dullness, man- 

 ifested by slowness of movement and an inclination to lag behind the 



