21 6 HABITS AND INSTINCTS OP ANIMALS. CHAP. VI. 



of a double series of hooks round the mouth, it adheres 

 to the intestines with the most astonishing firmness. 

 The common species (T". vulgaris} feeds also on the 

 chyle, and is from one to five yards long : it is like- 

 wise so tenacious as to resist the most violent remedies. 

 These, where the mouth is not armed with hooks,, are 

 more easily expelled than the others ; yet some of them 

 grow to an enormous and almost incredible length. 

 The T. tenella, or broad tape-worm, principally con- 

 fined to the inhabitants of Russia and Switzerland, is 

 said to have been found from six to forty yards long. 

 There are other races, where the annulose structure 

 seems obsolete, but which most authors concur in 

 placing in the same class as the former ; these are the 

 Ascarides, Tricocephalus, Filaria, Fasciola, anAFuria: 

 the last is a most deadly plague, happily confined to 

 the marshes of Sweden. 



(229.) The vermicular Ascarides are simple slender 

 worms, about half an inch long ; but they are generally 

 found in considerable numbers in the same person, and 

 occasion much pain and distressing symptoms, creeping 

 sometimes up into the stomach from the rectum, where 

 they usually reside : they are generally found in thin 

 people, and in children. The A. Lumbrico'ides is from 

 twelve to fifteen inches long, with a triangular mouth : 

 they are much larger and more disgusting than the 

 last, as they sometimes ascend into the stomach and 

 creep out of the mouth and nostrils. The Tricocephalus 

 Hominis somewhat resembles Ascarides : it inhabits the 

 intestines of children, and is frequently found in con- 

 siderable numbers within the caecum, giving to those 

 who are thus infested, a very sickly appearance. All 

 these intestinal parasites are found in Europeans ; and, 

 with but one exception, have occurred in this country : 

 how far they inhabit the natives of other regions, or 

 whether, as is most probable, the inhabitants of the 

 tropics are subject to other peculiar species, has not 

 been well ascertained. There is a dreadful worm, 

 however, found in both Indies, which is fortunately 



