d4i4i THE 2s^ATUEAL HISTORY EEYIEW. 



tapeworms were harboured by one of his patients. "We read, in an 

 authentic record, of more than five hundred Ascarids inhabiting the 

 alimentary canal of a child. But what are these to the thousands of 

 TricliincB which have been known in several cases to infest the muscles 

 of a single "host " ? 



It is true that some of the above may be looked upon as bad or 

 immature species, especially in such genera as Filaria. But human 

 Helminthology is yet young, and, doubtless, further researches will 

 soon bring to light new forms, to replace those which are lost by 

 being merged into others. 



With regard to comparative abundance, the species may be thus 

 arranged. Ten* have hitherto been observed in man's body once 

 only, and sevenf others on but two or three occasions respectively. 

 Eour species — Fasciola hepatica, Tcenia elliptica, Sclerostoma duode- 

 nale and Dracunculas loa appear to be of more frequent occurrence 

 than is usually supposed. The remaining ten species may fairly be 

 regarded as common human parasites. 



Some of the human Helminths are less frequent in man than in 

 other animals. Fasciola hepatica is the well-known liver ' fluke ' of 

 the sheep ; Distojna lanceolatum,X of the ox, and both Trematodes 

 occur in many herbivorous quadrupeds. Bothriocephalus cordatus is 

 common in dogs, within which also B. latus has been found. The 

 same may be said of Tcenia cucumerina, with which T. ellijptica of the 

 cat aj)pears identical ; Leuckart, however, is opposed to this opinion. 

 The strobiloid stages of the rare T. marginata, and, unhappily, the 

 too*common T. echinococcus. alike infest the dog and wolf, while the 

 sexless condition of the former is parasitic not only within man but 

 likewise within monkeys, squirrels, and various herbivora. Ascaris 

 mystax, which Dr. Cobbold has shown to include the A. alata of 

 Bellingham, is the round worm of the cat, and, like the CucuUanus 



* BUtojna crassiim, Tetrustoma renale, Hexathijriclium pinguicola, Tcenia acan- 

 thotrias, T. Jlavo-puuctata, T. nana, T. marginata, Bothriocephalus cordatus, 

 Filaria trachealis, and Eustrougylus gigas. It is very uncertain whether the last- 

 mentioned species be truly a human Helminth. Mr. Busk justly characterises the 

 accounts of its occurrence as " either of such remote date, or so imperfect, that it 

 is impossible from them to conclude whether the worm in question is really iden- 

 tical with that of the animals above mentioned [dog, polecat, etc.], or another 

 species of the same genus, or whether, as is not improbable, in all the human 

 cases some confusion has not arisen with the common round worm, Ascaris lunibri- 

 coides." (p. 918.) 



f Distoma lanceolatum, D. ophthalmohium, D. heterophyes, Hexathyridium 

 venarum, Ascaris mystax, Filaria lentis, and Strongylus hronchialis. 



X This species is said to occur also in the Cat, but the fact needs confirmation. 



