58 



VARIOUS FOKMS OF TAPEWORMS. 



EcMnococruK. — A third type of cyst known as Echinococcus 

 often assumes a great size. The sexual tapeworm that produces 

 this cyst is Tuniia echinococcus (Sieb.), fig. 16. This worm is 

 found in the dog, and is very prevalent. It is minute in size, 

 seldom exceeding one-fourth of an inch in length, and is composed 

 of never more than three elongated segments. The last segment, 

 which is much"- the largest, contains numbers of ova when 

 mature. The head is provided with a double row of hooks. 

 The colour is creamy-white, and they may be 

 found in great numbers in the fluid contents 

 of the dog's intestines, and are often seen 

 sticking round the anus. These worms are 

 derived from the cysts known as Echinococcus 

 ve.terinoruiii, found in herbivorous animals and 

 man, but especially in the Euminants. The 

 worms reach maturity in about a month after 

 the entry of the cysts into the stomach of the 

 dog. The cyst Echinococcus veteri no rum (Sieb.) 

 is the same as E. polymorphus of Diesiug. 

 They are to be met with in man, monkeys, 

 cats, dogs, rabbits, sheep, oxen, goats, horses, 

 deer, and many other animals ; but ruminants 

 and pigs are the greatest sufferers. Man in 

 certain districts, especially in Iceland and in 

 Mecklenburg, has often suffered seriously from 

 this so - called Hydatid plague. Although 

 Echinococcus is met with in all parts of the body, it is the 

 liver that is chiefly invaded : occasionally much pathologic 

 disturbance is also caused by them in the lungs and in the 

 kidneys. 



The ova of Twiiia echinococcus are passed out with the ripe 

 proglottis from the dog's bowels and get into the water. On 

 entering the herbivorous or omnivorous host the ova hatch, 

 and the embryos make their way tnd the portal systeHi to 

 the liver. They there produce small white cysts, which 



Fin. 16. —TAENIA 



ECHINOCOCCUS. 



A, Hook from same. 

 (Greatly enlarged.) 



