PARASITES FREE WHILE YOUNG. 



153 



fresh-water crustacean. Thus the parasite is received 

 by means of the water which is drunk; and this remark 

 is the more important since it will henceforth be only 

 necessary to make use of carefully filtered water in order- 

 to guard against it. At the end of six weeks, the presence 

 of the animal is re- 

 vealed by tumours, the 

 true nature of which 

 is not ascertained 

 at first ; then some 

 wounds appear, caused 

 not directly by the 

 worm, but indirectly 

 in consequence of the 

 dissemination of its 

 eggs. The Filaria at 

 last is so entirely atro- 

 phied that Professor 

 Jacobson, after having 

 seen it alive on one of 

 his patients at Co23enhagen, wrote to Blainville : '' This 

 Medina worm is not really a worm, it is a sheath full of 

 eggs." In fact, all the internal organs disappear and 

 nothing exists there except the eggs and their embryos. 



The Filaria is not allied to the Mermis, as was 

 formerly thought ; its organization is different, and its 

 organs become atrophied in a very different manner. 

 The Gordius ornatus, brought from the PhiliiDpines by 

 Professor Semper, has given us an opportunity, by dif- 

 ferent anatomical observations, to correct many errors, 

 especially with respect to the digestive apparatus 

 (Grenacher). The Filaria immitis is a species found by 



Fig. 32. — Younff Filaria of Medina ; 1, 

 Anterior extremity ; c. Mouth ; 2, Caudal 

 extremity ; d. Anus ; 3, Section of the 

 Body. 



