233 DISEASES DUE TO INTERNAL PAEA6ITES. 



lodging in the respiratory cavity of that mollusk. Here it be- 

 comes encysted, contracting into an oval mass, which grows 

 rapidly. At this stage it is called a sporocyst. This sporocyst 

 splits up into from five to eight bodies, called rediae, which are 

 about 2 mm. in length, these leaving the cyst one by one. 

 These rediae each one of them develop within themselves fifteen 

 to twenty cercariae, which are thrust out in turn through an 

 orifice under the neck of the rediae. 



These cercariae are what escape from the snail, being scat- 

 tered broadcast in its wanderings. After a short time they lose 

 their tails, and again become encysted, the contents of these 

 cysts being attached to blades of grass, etc., are swallowed by 

 the sheep or other animal, the gastric juices acting on it break 

 the covering, setting free the yoimg flukes in the stomach and 

 duodeneum, from which they gain the biliary ducts, and pass up 

 them to the liver, where they grow into adult hermaphroditic 

 parasites able to give origin to other generations of young. 



The life cycle of this parasite is as wonderful as any occur- 

 ring in nature, at least seventy-five young flukes under suitable 

 circumstances being able to develop from a single egg. 

 preventive Creatmetit. 



"We cannot do better than print verbatim Thomas' formu- 

 lated rules of prevention against this parasite, founded on its life- 

 history, as follows: 



"1. All eggs of the liver-fli^ke must be vigorously de- 

 stroyed. Manure from rotten sheep or other infected animals 

 must not be put on wet ground. As the liver and intestines con- 

 tain the eggs, those too must be destroyed or put in the compost 

 lieap. The manure of affected animals should not be stored 

 where there is a drainage from it to the neighboring grass. It 

 should be mixed with lime and salt before being spread on 

 meadows or cultivated fields. 



"2. If sheep are infected, let them be sent to the butcher 



