Evolution / by Patrick Geddes and J. Arthur Thomson.

  • Patrick Geddes
Date:
[1911?]
Catalogue details

Licence: Public Domain Mark

Credit: Evolution / by Patrick Geddes and J. Arthur Thomson. Source: Wellcome Collection.

    109/264 (page 105)
    and his liver changed from its natural brown almost into the likeness of a tangle of white worsted, of which each thread is a tape¬ worm. Neither frog nor lizard, serpent nor bird, escapes; indeed birds are peculiar suf¬ ferers, witness the too common 44 gapes ” of poultry, a choking of the windpipe by thread¬ worms, and the numerous parasitic worms which Mr. Shipley’s labours have discovered in the well-nigh sacred grouse. Of ticks the shepherd is only beginning to know the full dangers, as of fleas man himself. Apart from bacterial and protozoan pests, as yet beyond counting, man is debited by the parasitologist with at least sixty species; some reckon twice as many. The amazingly varied methods of Nature for the diffusion of para¬ sites are among the very strangest disen- tanglements of the web of life, but into the stories of these adventures in search of mis¬ chief we cannot enter here : enough if we note the stupendous rate of multiplication by which the many chances against finding the proper host are constantly met; thus the common tape-worm of man has been calculated to produce eighty-five million ova during its two years’ existence. It is an interesting inquiry whether the large numbers of so-called species of thread-