Licence: Public Domain Mark
Credit: Hydatid disease in its clinical aspects / by James Graham. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
22/366 (page 6)
![some cases worms which had a free existence, and which resembled in appearance the parasitic forms. The discovery by Linnd of a tapeworm in fresh water seemed to give weight to this view. It was not known, however, by this naturahst that the Bothrio- cephalus or Schistocephalus soHdus inhabits the body cavity of the stickleback, but leaves it at a certain stage of its development, and after passing some time in the water is eventually swallowed by a waterfowl. Linne regarded this free form as an incomplete speci- men of the Bothriocephalus latus so common in the human subject, and inferred that it was swallowed by man. He also claimed to have found living in a free state the liver fluke of the sheep and the Oxyuris of the human subject. It was, however, shown later that he had mistaken a Planarian and one of the free-living AnguilMidse for these parasites. Linne's hypothesis seemed very feasible, and was commonly accepted, as it offered an easy explanation of the origin of human parasites ; but the researches of several helminthologists so increased the number of parasitic species, and, as all attempts to find them in a free state failed, the theory of free existence had to be abandoned, especially when it was shown that Linne was wrong in supposing that certain worms which he found in water were identical with some found in the human subject, whereas they were only similar in appearance in some respects, but of entirely different species. It was Pallas who subsequently ]3ut forth the theory that the Entozoa resembled other animals](https://iiif.wellcomecollection.org/image/b2191199x_0024.jp2/full/800%2C/0/default.jpg)
