38 ENTOZOA FOUND TN MAN. 



Distomum Ophthalmohium. 



Tills is a very small trematode worm, of which 

 species four specimens were observed by Gescheidt 

 and Ammon in the eye of an infant affected with 

 congenital cataract. 



Chapter IV. 

 NEMATOIDEA. 



The worms included in this class have a long filiform, 

 or fusiform, body, wliich is covered by a strong integu- 

 ment, composed of areolar tissue. The mouth is 

 terminal, or nearly so ; the intestine is straight, and 

 runs throughout the whole length of the body ; and 

 the two sexes are separate. 



The circulatory system is always rudimentary, 

 even in those nematoidea which are most developed ; 

 and, although some writers have described a nervous 

 system, its existence is very doubtful. 



No respiratory apparatus has ever been ascer- 

 tained to exist in any of these animals. 



One or two longitudinal canals, which open upon 

 the ventral surface not far from the mouth, most 

 probably represent an excretory system. These 

 canals are well-marked m the Anchylostomum duode- 

 nale, and in some of the StrongyH, and of the 

 Ascarides. 



The digestive apparatus is always very simple. 

 The mouth differs in its conformation in the various 

 genera of the Nematoidea, and it is often furnished 



