. The physiology of the domestic animals; a text-book for veterinary and medical students and practitioners. Physiology, Comparative; Domestic animals. 74 PHYSIOLOGY OF THE DOMESTIC ANIMALS. form of an irregular net-work, as represented in Fig. 46. These proto- plasmic threads are the seat of changes, both of form and position. The single filaments may become thicker or thinner, or a new filament may spring out from and enter and unite with adjoining filaments, or may undergo division into several others, the process being analogous to that already described as characterizing the amoeba. In ad
. The physiology of the domestic animals; a text-book for veterinary and medical students and practitioners. Physiology, Comparative; Domestic animals. 74 PHYSIOLOGY OF THE DOMESTIC ANIMALS. form of an irregular net-work, as represented in Fig. 46. These proto- plasmic threads are the seat of changes, both of form and position. The single filaments may become thicker or thinner, or a new filament may spring out from and enter and unite with adjoining filaments, or may undergo division into several others, the process being analogous to that already described as characterizing the amoeba. In addition to this motion in the cell-contents, rotatory movements may also be seen to take place in the protoplasm which is in contact with the walls of the cell, rotation occurring in a constant direction and with almost uniform rapidity around the cell-nucleus, the imbedded chlorophyll and starch- granules rotating in a mass without airy decisive change in their relative positions. Such rotatory move- ments are seen in the leaf-cells of the Yallisneria, and various other plants. Similar motions are also seen in the paramoecium and other infusoria. In young animal cells the same character of movement is often present; often when a membrane is absent or is very flexible the pro- toplasmic movements cause a change in the entire shape of the cell, and the motion so produced cannot be distinguished from those of free protoplasm. Occasionally protoplasm be- comes free by escaping from the interior of cells, such as the so-called plasmoids of myxonrycetes, in which not only an internal granular move- ment but also a change of external shape may be made out. Similar phenomena are also seen in those organisms which consist of masses of free protoplasm, such as the monera, rhizopods, polyps, and infusoria. Such protoplasm possesses in an eminent degree the property of contractility,—a term originally applied to striped and unstriped muscles. The changes in form of masses of free protopl
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