Parasitism : organic and social / by Jean Massart and Émile Vandervelde ; translated by William Macdonald ; revised by J. Arthur Thomson.

  • Jean Massart
Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: Parasitism : organic and social / by Jean Massart and Émile Vandervelde ; translated by William Macdonald ; revised by J. Arthur Thomson. Source: Wellcome Collection.

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    animais show more or less degeneration according to the period at which tliey avail themselves of the nourishment afforded by their liost. Thus the Isopod crustaceans, which live in the mouths of fishes and take their food just as it bas been seized, before it lias been subjected to any pro- cess of digestion, hâve retained ail their digestive organs. To this type of parasite Van Beneden has applied the terni commensal. Worms and other animais which infest the alimentary canal illustrate a more advanced stage of parasitism ; they take food which has been more or less digested, and therefore they are able to dis- pense with, and are generally without, those organs whose function it is to render the food diffusible. Finally, those parasites which live in the blood and the tissues, and thus obtain completely assimilated material, are in most cases without any digestive System. They are fed by diffusion from the nutritive medium in which they are bathed. ((b) Certain saprophytic, coprophagous, or necropha- gous species may become completely transformed into parasites ; others, while preserving their original mode of nutrition, may exhibit characters which link them more or less closely to parasites. Thus the spores of certain Ascomycetous Fungi which live on dung can only germinate if they bave
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