228 ANIMAL PABASITES AND MESSMATES. 



It is only found in Eussia, Poland, and Switzerland, and 

 the limits of the places which it inhabits are perfectly 

 defined. Siebold, during his stay at Konigsberg, could 

 determine from the nature of the worms, whether the 

 patient who consulted him lived on one side or the other 

 of the Vistula. 



A Eussian naturalist, Dr. Koch, thoroughly Btudied 

 this interesting worm and its evolution. He says that 

 this cestode is rare at Moscow, while at St. Petersburg, 

 Eiga, or Dorpat it is common. If this be really the case, 

 it must doubtless be attributed to the fact that in one 

 place the inhabitants drink spring water, and in the 

 other water from the river. 



A very curious circumstance is the actual rarity of 

 the Bothriocephalus among the inhabitants of the shores 

 of the Lake of Geneva, though formerly it was very 

 common there. This diminution, if we may not call it 

 disappearance, is due to the change which has been 

 made in the construction of water-closets, all of which 

 formerly emptied themselves into the lake, so that the 

 embryos were hatched in the water, and persons were 

 infested by them through drinking it. At present the 

 refuse of the towns is carefully collected for the purpose 

 of manuring the land. This is the result of the advice 

 of Mons. de Candolle, half a century ago;, for this 

 naturalist clearly understood how great was the loss to 

 agriculture from the neglect of this fertilizing agent. 



The itinerary of this tape-worm is simple. It passes 

 from man to the water under the form of an egg, or of 

 a proglottis ; and from the water to man in the shape of 

 a ciliated embryo. In this manner it is introduced with 

 the water that is drunk. The Bothriocephalus, like 



