THE DIGESTIVE SYSTEM 69 



infestation has occurred and by properly disposing of 

 the excrements of swine that are infested. 



Echinococcosis 



The invasion of the liver of swine with the larvae of 

 the Tsenia echinococcus is quite common. In the Old 

 World from one per cent to seventy per cent of the 

 swine are reported to be so infested. 



The mode of entrance into the liver is by way of the 

 portal system, the embryo passing through the intestine 

 into capillaries that empty into radicles of the portal 

 vein. Infestation is derived from food or drink con- 

 taminated with the feces of dogs, that harbor the Tsenia 

 echinococcus. 



Lesions. The liver is enlarged; the degree depending 

 upon the number of parasitic cysts it contains. Gerard 

 observed an infested swine liver that weighed 110 pounds. 

 The surface of the liver may be very irregular due to 

 the presence of the cysts near the capsule or just beneath 

 the capsule. The cysts, which vary in size from a pear 

 to a small hen's egg, are the primary lesions and may be 

 polymorphous or multilocular. The polymorphous cysts 

 are surrounded by a fibrous capsule inside of which the 

 true cystic membrane is found and upon which daughter 

 and granddaughter cysts and the head of the future 

 tapeworm may be seen. The cyst contains a pale, 

 straw-colored, limpid serum. The multilocular cyst is 

 a mass of single cysts developing on the outside of the 

 true cystic membrane instead of developing on the inside, 

 as in the polymorphous cyst. The cysts necessarily dis- 

 place and by pressure destroy liver tissue. Old cysts 

 contain a cheesy or caseous substance; in some instances 

 a purulent collection. 



Symptoms. Clinical evidence of the presence of 

 hepatic echinococcus cysts are usually wanting. A few 

 cases of ascites associated with hepatic echinococcosis 

 have been recorded. There may be icterus and some 

 digestive disturbance. 



