102 



BOARD OF AGRICULTURE. 



few days. The external skin, with the cilia, is then cast off, 

 liberating a very different looking embryo or larva, which is 

 provided with six boring hooks, similar to those of the em- 

 bryos of ordinary tape-worms. Their subsequent history has 

 not been ascertained, but it is probable that they enter some 

 fish (most likely trout and salmon) and become encysted 

 among the muscles, and that persons who eat imperfectly 

 cooked or raw dried fish get the parasite in that way. 



It is remarkable that this species is not known to be indig- 

 enous in any but European countries, and even in Europe it 

 is peculiar to certain districts. It is particularly common in 

 certain parts of Switzerland. In Geneva it is said that about 

 one-fourth of all the inhabitants are afflicted with this worm. 

 It occurs also in some parts of Russia, Poland, and Prussia. 

 In America it has only been observed in emigrants from 

 Europe, and in persons who have traveled in the European 

 countries where it naturally occurs. It causes similar symp- 

 toms and is removed by the same remedies as the common 

 tape -worms. 



TREMATODE WORMS. 



The Liver-fluke of Sheep and Cattle (Fasciolahepatica Linn.). 

 This common and notorious parasite has a very flat body, 

 different on the two sides, and more or less oval in form, the 

 anterior end suddenly narrowing to a sort of neck, which 

 tapers off to the mouth end, where it is either rounded or 

 pointed. The posterior end of the body is Figure 78. 

 somewhat tapering, but blunt. Ordinary speci- 

 mens are about three-quarters of an inch long 

 and half an inch wide, but large ones become 

 an inch and a quarter long and three-quarters 

 broad. While living they often curl up the ends 

 of the body, toward the lower side. The color 

 is pale brownish or greenish yellow, sometimes 

 with a faint rosy tint. At the anterior end of 

 the body there is a small, cup-shaped sucker, at 

 the bottom of which the mouth is situated 

 (Figure 73, a) ; near the origin of the neck- 

 like portion, on the middle line of the lower side, there is 



