The study of animal life / by J. Arthur Thomson.

  • John Arthur Thomson
Date:
1896
Catalogue details

Licence: Public Domain Mark

Credit: The study of animal life / by J. Arthur Thomson. Source: Wellcome Collection.

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    feet of land chosen at random, Mr. Alvan Millson collected the worm-casts of a season and found that they weighed when dry iof lbs. At this rate about 62,233 tons of sub- soil would be brought in a year to the surface of each square mile, and it is also calculated that every particle of earth to the depth of two feet is brought to the surface once in 27 years. We do not wonder that the district is fertile and healthy. Devouring the earth as they make their holes, which are often 4 or even 6 feet deep ; bruising the particles in their gizzards, and thus liberating the minute elements of the soil; burying leaves and devouring them at leisure ; preparing the way by their burrowing for plant roots and rain-drops, and gradually covering the surface with their castings, worms have, in the history of the habitable earth, been most important factors in progress. Ploughers before the plough, they have made the earth fruitful. It is fair, however, to acknowledge that vegetable mould sometimes forms inde- pendently of earthworms, that some other animals which burrow or which devour dead plants must also help in the process, and that the constant rain of atmospheric dust, as Richthofen has especially noted, must not be overlooked. In 1777, Gilbert White wrote thus of the earthworms— “The most insignificant insects and reptiles are of much more consequence and have much more influence in the economy of nature than the incurious are aware of. . . . Earthworms, though in appearance a small and despicable link in the chain of Nature, yet, if lost, would make a lamentable chasm. . . . Worms seem to be the great promoters of vegetation, which would proceed but lamely without them, by boring, perforating, and loosening the soil, and rendering it pervious to rains and the fibres of plants ; by drawing straws and stalks of leaves and twigs into it ; and, most of all, by throwing up such infinite numbers of lumps of earth called worm- casts, which, being their excrement, is a fine manure for grain and grass. Worms probably provide new soil for hills and slopes where the rain washes the earth away; and they affect slopes probably to avoid being flooded. . . . The earth without worms would soon become cold,' hard-bound, and void of fermentation, and con- sequently sterile. . . . These hints we think proper to throw out, in order to set the inquisitive and discerning to work. A good mono-