232 ento-parasites atstd hygiene. 



it in most cases is the pig; it lives also in rats, dogs, 

 cats, foxes, etc. Ordinarily it is found in encysted stage 

 in the muscles of different animals. In these muscles, 

 and in these only, the observer notices numerous small 

 v^^hite knots, capsules, in which the worm is seen rolled 

 up in the form of a spiral. In this form and shape the 

 trichina is able to wait a long time, sometimes ten or 

 twenty years, even more, and this form is also nearly 

 always the one being observed. Yet this does not repre- 

 sent its definite state, only one of immaturity. As soon 

 as such meat studded with encysted trichines is eaten 

 (even if it should be slightly boiled, the worms will 

 remain alive in their capsules), they leave their cysts 

 in the stomach, grow to maturity within a few days, and 

 produce a progeny numbering many thousands for each 

 single female. These young parasites make haste to 

 leave the alimentary canal in enormous quantities, bore 

 through its walls,and arrive finally in the voluntary mus- 

 cles, where they come to rest. They live on the sub- 

 stance of the same and cause them to decay and perish. 

 During their growth they roll up in a spiral, surround 

 themselves with a capsule of a lime-like nature, and be- 

 come again encysted trichinas. The other forms which 

 became mature in the intestines have correspondingly 

 the name intestinal trichinas ; they soon perish after hav- 

 ing produced their eggs, at all events they play a much 

 less important role concerning their mode of life than 

 their early immature forms. Since we know this devel- 

 opment of the trichina, we are able to put a stop to its 

 introduction into the human body — in other words, to 

 prevent trichinosis. This is one of the first and most im- 

 portant practical results which these researches in para- 

 sitism have produced, for which we all must be eminently 

 thankful to such investigators as Leuckart (the " in- 

 ventor" of trichinas), Virchow, Zenker and others. But 

 only in our day have we succeeded in banishing this 



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