250 



THE TAPEWORMS 



pinhead to a pea, with few and scattered heads. These masses 

 of vesicles, known as " multilocular " cysts, may be six inches 

 or more in diameter; they are most frequently found in the liver. 

 Unless surgically removed they usually prove fatal sooner or later. 

 The fact that the " multilocular " cysts are not found in Ice- 

 land or Australia where the ordinary cysts are so common, and 

 that they occur to the almost total exclusion of the ordinary 

 kinds in some countries, especially in parts of Germany, suggests 

 that they may belong to a different species indistinguishable 

 from E. granulosus in the adult state. 



The great size to which hydatids may grow makes them danger- 

 ous on account of the mere mechanical damage they may do, 

 especially if they occur in such organs as the heart, brain, kid- 

 neys or liver. The liver of an ox containing hydatids has been 



known to reach ten times its normal 

 weight, and to be of such large size 

 as to cause much mechanical injury 

 to neighboring organs. But more 

 dangerous than the mechanical injury 

 is the possibility that the vesicles, 

 hemmed in by restraining tissues, may 

 burst and liberate into the tissues the 

 poison-bearing liquid which fills them. 

 Hydatids may grow persistently for 

 many years. There is one case on 

 record where a swelling had gradually 

 developed during 43 years over a large 

 FIG. 97. Echinococcus cyst portion of the face of a woman, and 



in liver of man. (After Huber was as l ar o;e as a child's head. When 

 from Stiles.) . , . 



removed by an operation, this was 



found to be a hydatid. Ordinarily growth does not increase 

 beyond the size of a baseball. The only treatment is a surgical 

 operation. 



The conditions which exist in places where hydatid disease in 

 man is common gives us an idea of what to avoid in order to pre- 

 vent infection. In Iceland from 30 to 100 per cent of the dogs in 

 different regions are said to be parasitized by Echinococcus. A 

 large proportion of the sheep and many cattle are infested with 

 the hydatids. The dogs are fed on the uncooked entrails and 

 waste meat of slaughtered animals, and the dogs in turn are 



