268 DISEASES DUE TO HELMINTHS 



site bores its way to the liver or other organs, g•ro^\ s and forms a cyst 

 of three layers : — 



(i) A thin layer or endocyst with granular, nulceated cells. 



(2) A thick outer layer or ectocyst which is laminated and opaque. 



(3) A connective tissue layer about the whole. 



The inner layer of cells in cattle forms numerous hollow brood 

 capsules called the E. cysticus sterilis, which have the endocyst external 

 and the ectocyst internal. Of these brood capsules, heads develop 

 called E. cysticus fertilis, but these more commonly occur in domesti- 

 cated animals. 



In man daughter-cysts appear between the strata of the cuticle into 

 which endocystic cells have found their way and formed cysts. 



These latter may grow and escape internally or externally. If 

 externally they lie between the capsule and the mother-cyst and form 

 E. hydatidosus exogenus, or if internally they fall into the mother- 

 cyst and are then known as E. hydatidosus endogenus. These 

 •daughter-cysts may remain sterile or produce brood capsules and 

 heads which are then called grand-daughter-cysts. The wall of the 

 mother-cyst may disappear and leave the daughter-cysts free. 



PATHOGENICITY. 



The cysts grow slowly so that the organs have time to accommodate 

 themselves somewhat to the changes. If the organ cannot expand the 

 symptoms are early and marked. If the cyst ruptures the fluid will 

 cause urticarial symptoms, rigors, local pain, and tenderness. 



The cystic fluid is toxic and a sudden discharge of a large cyst 

 into the abdominal cavity may be so toxic as to kill, acting upon the 

 heart like prussic acid. 



It may rupture into the lung and drown the patient. 



The cysts may become fatty, cheesy, and calcified. They may 

 become secondarily infected. 



ECHINOCOCCUS MULTILOCULARIS. 



This causes the rnuUilocuJar form of hydatid disease. 



DISTRIBUTION. 



South Germany, Switzerland, Austria, Russia, and Serbia. 

 It is absent in Iceland, Australia, and the European districts where 

 the cystic form is met with. 



It occurs in animals and man. 



MORPHOLOGY. 



The cysts are composed of parenchymatous tissue internally and 

 ■externally. There is no third outer fibrous coat. 



These produce not only scolices but immature amoeboid embryos 



