346 THE NATURAL HISTORY REVIEW. 



been obtained ? Leuckart would attribute their presence, when 

 occurring in large numbers, to a process of ' self-infection.' T. acan- 

 thotrias, T. marginata and T. ecTiinococcus have as yet been detected 

 in man in the scolex state alone. His other Cestoids are only known 

 in their strobiloid form. 



The relative frequency of human Helminths varies much in diffe- 

 rent regions. According to Davaine, at least half the population of 

 Paris are infested by Tt^ichocephalus cUspar. Kaschin writes that " In 

 Irkutsk, the Burates stationed there as Cossacks, and who, in part, 

 have been away from their homes for many years, are, almost all 

 of them, infested by tape- worms ; some individuals harbouring as ' 

 many as fifteen specimens at a time. In one hundred and thirty 

 post-mortem examinations only two bodies were found entirely free 

 from these parasites, and among five hundred other persons, treated 

 in hospital, the existence of these entozoa was demonstrated in all." 

 And in Iceland the common hydatid is so numerous, that Schleisner 

 out of 327 patients, encountered 57 who were suftering from it. 

 In all such instances, where a notable superabundance of Entozoa 

 occurs, the explanation is not far to seek. "We find, when we examine 

 the habits of those infested, a neglect of the ordinary means of pre- 

 vention. Thus, the Cossacks above referred to, " are herdsmen, and 

 " feed almost exclusively upon flesh, especially that of calves, sheep, 

 " camels, and horses ; they neither clean the meat of these animals 

 " properly, nor cook it completely, and, moreover, they eat from 

 " tables which immediately before have served for the purpose of 

 " cutting up the flesh. The tables are just as little familiarized with 

 " the application of water, as are the dishes and the people them- 

 " selves ; in other words, they are never cleaned. Fat, liver, and 

 " kidneys are eaten quite raw, and diseased animals are as much 

 " relished as half-rotten carcases. Moreover, these Burates are so 

 " voracious that any two of them can demolish a one-year old lamb 

 " at a single meal." 



Human Helminths, like other animals, obey the laws of geogra- 

 phical distribution. The two species of Dracunculus are found 

 only in some tropical regions, while the broad tape-worm restricts 

 its range to certain parts of the continent of Europe. Bilharzla^ 

 is confined to Africa. Some might choose to state that these para- 



• This parasite is also remarkable as affording, in common with one or two 

 species of Distoma proper, the rare example of a unisexual Trematode. 



