250 



THE TAPEWORMS 



The great size to which hydatids may grow makes them 

 dangerous on account of the mere mechanical damage they may 

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

 kidneys or liver. The liver of an ox containing hydatids has 



been known to reach ten times its nor- 

 mal weight, and to be of such large 

 size as to cause much mechanical in- 

 jury 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 wa s as large as a child's head. When 



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 

 allowed to run at will over the pastures, dropping the egg-laden 

 proglottids with the faeces in places where the water or food of 

 the stock may be infected. Dogs are allowed the free run of 

 the houses, are given unbounded liberty in playing with children, 

 and not infrequently eat from the same dish as their human 

 companions. The resulting prevalence of Echinococcus in both 

 dogs, stock and man is hardly to be wondered at. 



The precautions which should be taken to prevent the spread 

 and to bring about the control of this disease may be sum- 

 marized as follows: (1) avoidance of too great familiarity with 



