The parasites of man, and the diseases which proceed from them : a text-book for students and practitioners / by Rudolf Leuckart ; translated from the German, with the co-operation of the author, by William E. Hoyle.

Date:
1886
Catalogue details

Licence: Public Domain Mark

Credit: The parasites of man, and the diseases which proceed from them : a text-book for students and practitioners / by Rudolf Leuckart ; translated from the German, with the co-operation of the author, by William E. Hoyle. 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.

    44/808 (page 12)
    connective tissue, the brain and eye, and many other localities; Uchinococcus is found in the liver, spleen, kidney, lung, hones, nervous centres, beneath the skin, and, in short, almost everywhere in the human body. Similarly Filaria papillosa of the horse is not only found in the peritoneal membrane, but also in the peripheral connective tissue of various parts of the body, and occasionally in the body-cavity, inside the skull and vertebral column, sometimes even in the eye, either in the outer layers, the anterior chamber, or the vitreous body. The same principle holds good in regard to the relations of a parasite to its host. Some species are limited to a single host; others, again, are parasitic upon several animals, not merely at different periods of their existence—passing their youth in the body of one animal, and attaining their maturity in that of another—but also during the same phase of development. In the first group may be reckoned among human parasites, Pediculus capitis, Bothriocephalus latus, and Oxyuris vermicularis; also Taenia crassicollis of the cat, and Echinorhynchus gigas of the pig. To the second group belong by far the greater number of parasites, such as Strongylus gigas, which is found in many Carnivora—in the genera Ganis, Mustela, Nasua, &c, in the horse, the ox, and in man; Trichina spiralis, which not only infests man, the pig, and the rat, but also the hedgehog, fox, martin, dog, cat, rabbit, ox, and horse, and may be trans- planted even to birds. Distomum hepaticum has also a very wide distribution among warm-blooded animals, being found in most Eumi- nantia, Perissodactyla, Pachydermata, and Eodentia, and also, in the kangaroo, in man, &c. Although it is a general rule that a para- site infests several distinct animals, it is equally true that the distribution of parasites is governed by certain laws. The examples just cited show this clearly. The various animals which are infested by one and the same parasite are always more or less closely related to each other. It is most usual to find that the related species of a given genus, or the genera of a given family, harbour the same para- sites ; there are, indeed, only very few exceptions to this rule, such as Trichina spiralis. But even in these rare cases a certain relation can be observed between the different hosts ; and a parasite which in the same stage of its existence infests sometimes a mammal or a fish, sometimes a mollusc, is quite unknown. This fact becomes more evident when we examine not merely the number of hosts in which a given parasite is met with, but also the statistics of the distribution of parasites, and discover the number of times which it is found in each host; for instance, in other words, Distomum hepaticum is only rarely found in man, the kangaroo, and rodents, while it is commonly met with in ruminants, especially in the sheep. The same holds good