272 THE MICROSCOPE. 



With the exception of one family, all the worms included in the 

 order Nematoidea are parasitic in the bodies, and principally in the 

 intestines of other animals ; they are, in fact, amongst the most common 

 and the most injurious of Entozoa. 



\ This order includes the common Ascaris, or Sound-worm of the 

 human subject, as well as the little Thread-worms (Oayuris) which are 

 often so troublesome to children ; the Strongylus gigas, a worm some- 

 times attaining a length of two or three feet, and the thickness of a 

 garden worm, which usually inhabits the kidneys of swine, but some- 

 times finds its way into the same organ in man. This tremendous 

 worm, by destroying the organ in which it has taken up its abode, 

 frequently causes the death of its host. 



In this order we also place the Anguillulidce, the so-called Eels of 

 paste and vinegar. These are minute thread-like worms, exhibiting 

 distinct digestive and generative organs, which occur often in great 

 numbers in putrefying substances. 



This order also includes the dreaded Guinea-worm (Filaria medi- 

 nensis, fig. 117), which appears to occur in most parts of tropical 

 Africa. This worm lives in the cellular tissue beneath the skin of 

 man, confining its attacks principally, though not exclusively, to the 

 lower extremities, where it often produces considerable pain. It is 

 said occasionally to attain a length of twenty or thirty feet ; but its 

 average length is five or six. It is extracted by winding it very slowly 

 upon some object, an operation in which great care is said to be neces- 

 sary, as if the worm be broken, its fluids produce a very painful effect. 



In man, and some of the lower animals also, the muscles are fre- 

 quently attacked by Cysticercus cellulosce ; a well-known disease in the 

 pig is caused by them, it is then called by pork-dealers " measly pork." 

 Becent researches have shown this Entozoa is but the larva of Tcenia. 



The EcJdnococcus, another Entozoa, is found in cysts, both in the 

 body of man and sheep. 



Fig. 118 represents a bunch taken from the liver of a boy who died 

 in Charing-cross Hospital from rupture of the liver, occasioned by the 

 wheel of an omnibus passing over him. The simple cysts containing 

 these animals are always situated in cavities in the interior. These 

 cavities may be situated in any part of the tissues or organs of the 

 body ; they are more frequently found in the solid viscera, and especi- 

 ally in diseased livers. 



Mr. Busk, who has examined several of these cysts, says : " When 

 a large hydatid cyst, for instance, in the liver of the sheep, very 

 shortly after the death of the animal, is carefully opened by a very 



