TAPE-WORMS 457 



possible by the abundant food-supply of the parasite and the ease with 

 which this is obtained. Further, we also see how the disadvantages of a 

 parasitic mode of life (uncertainty as to the fate of the eggs) is balanced 

 by its advantages (a rich supply of nourishment, and consequently a 

 large number of eggs). 



D. The Tape- Worm in its Relations to Man. 



Though the tape-worm is far less dangerous to man than the trichina, 

 it nevertheless gives rise to all kinds of digestive disturbances, and is, 

 at any rate, a troublesome messmate, whom it is well to get rid of as 

 quickly as possible. It may, on the other hand, become extremely 

 dangerous when its eggs by some accident or other happen to get into 

 the human stomach, since in this case the proscolex develops into the 

 cysticercus in the body (especially in the brain and eyes) . Hence no one 

 should ever eat raw or insufficiently boiled or roasted meat, should 

 practise the greatest cleanliness, and be specially careful of keeping 

 human excreta away from himself and from pigs. 



Other Species of Tape- Worm. 



By the same means we shall also protect ourselves from other species 

 of tape-worm, two of which especially are frequently found in man — 

 viz., the Unarmed or Beef Tape-Worm {Tcenia saginata), the cysti- 

 cercus of which is found in the ox and other horned cattle (called 

 " unarmed " owing to absence of hooks) ; and the Broad or Russian 

 Tape-Worm (Bothriocephalus latus), the intermediate hosts of which 

 are the pike and the burbot. Hence the latter is found specially 

 frequently in (European) countries where much fish is eaten (name 

 some). It attaches itself to the intestine of its host only by the help of 

 two elongated suckers. 



Our most faithful companion, the dog, houses two extremely dangerous 

 species of tape-worm. The cysticercus (" blister ") of the first, the 

 Blister Tape-Worm, lives in the brain (especially) of sheep, in which 

 animal it gives rise to the disease known as " staggers." In order to 

 stamp out this disease from the herd, or to prevent it from spreading, it 

 is, of course, necessary carefully to destroy the brains of animals which 

 have died from it. The other species of dog tape-worm, Tcenia echino- 

 coccus, is also a very dangerous guest. It is only from f to f inch 

 long, and consists of only three or four proglottides. The cysticercus, 

 on the other hand, which lives in the most widely different organs of 

 domestic animals and man, may sometimes reach the size of a man's 

 head. Upon its wall, which is very thick, are formed what are known 



