ECHINOCOCCUS DISEASE 



527 



they breed m the capillaries of the portal circulation explains the frequent 

 implication of the liver. Often the embryos lodge permanently in the mesen- 

 teric glands. Others, by means of the lymph-vessels, or by various avenues 

 of communication, invade the peritoneal and pleural cavities ; others enter the 

 thoracic duct, thence find their way into the Jugular vein and to the right 

 heart, and are retained in the lung or are distributed to near or even distant 

 organs. 



After the echinococcus embryo has reached its destination it develops very 

 slowly; we would digress too far if we described the individual phases of its 

 development. 



After the lapse of weeks or months, we again find the echinococcus in a 

 round white cyst which gradually increases in size. Its walls are composed 

 of a characteristically layered cuticula and a parenchymatous layer. After a 

 certain time the latter shows upon its inner surface the so-called breeding 

 capsules, which hang upon a short pedicle from the parenchymatous layer, and 

 are surrounded by a transparent fluid not containing albumin. Some of the 

 breeding capsules develop internally, some externally, 

 producing echinococcus heads, the so-called scolices. 



Fig. 50. — Tenia Echinococcus. 

 Greatly enlarged. 



Fig. 51. — Head op the Echinococcus: 

 a, with projected, and b, with retracted, head. 



In many cases daughter-cysts are formed. These originate from embryos 

 which probably represent original parts of the parenchymatous layer, but have 

 remained intralamellar. They lead to cyst formation surrounded by its ovni 

 cuticula. Gradually bulging inward, they finally reach the cyst cavity. We 

 then speak of echinococcus hydatidosus or endogenus. This endogenous 

 daughter-cyst development is opposed by the exogenous, which occurs mostly 

 among our animals used for food, but may even occur in man. The daughter- 

 cysts may later form other cysts. The contents of the cyst are colorless and 

 clear, or slightly opalescent. The fluid contains albumins which are not pre- 

 cipitated by boiling, also common salt, succinic acid and sugar; occasionally 

 inosite, leucin and tyrosin. 



The echinococcus cyst at any stage of its development may become sterile ; 

 i. e., the formation of scolices (acephalocysts) ceases. Not rarely the echino- 

 coccus worm becomes diseased and dies. The fluid becomes turbid, the walls 

 of the cyst collapse, the parenchymatous layer softens and fatty degeneration 



