Page:The Formation of Vegetable Mould through the Action of Worms (1881).djvu/263

 therefore cannot have the power of utilising stones.

During the grinding process, the particles of earth must be rubbed against one another, and between the stones and the tough lining membrane of the gizzard. The softer particles will thus suffer some attrition, and will perhaps even be crushed. This conclusion is supported by the appearance of freshly ejected castings, for these often reminded me of the appearance of paint which has just been ground by a workman between two flat stones. Morren remarks that the intestinal canal is "impleta tenuissimâ terrâ, veluti in pulverem redactâ." Perrier also speaks of "l'état de pâte excessivement fine à laquelle est réduite la terre qu'ils rejettent," &c.

As the amount of trituration which the particles of earth undergo in the gizzards of worms possesses some interest (as we shall hereafter see), I endeavoured to obtain evidence on this head by carefully examining many of the fragments which had passed