. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. PROTOPLASM AND THE CELL 27 Structure of Protoplasm. — Protoplasm, when viewed under a high magnification of a compound microscope, is a grayish, almost fluid mass, seem- ingly almost devoid of any structure. A careful observer will, however, find that the material seems to be made of a ground mass of fluid with innumer- able granules of various size and form floating in the fluid portion. Other observers believe protoplasm to consist of a fluid groundwork with in- numerable tiny threads sca
. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. PROTOPLASM AND THE CELL 27 Structure of Protoplasm. — Protoplasm, when viewed under a high magnification of a compound microscope, is a grayish, almost fluid mass, seem- ingly almost devoid of any structure. A careful observer will, however, find that the material seems to be made of a ground mass of fluid with innumer- able granules of various size and form floating in the fluid portion. Other observers believe protoplasm to consist of a fluid groundwork with in- numerable tiny threads scattered through it, each thread being more or less firmly united with other threads of the mass. Still other scientists hold that protoplasm has essentially the structure of an emulsion or froth or foam. To them the fine structure resolves itself into a collection of very minute bub- bles. Doubtless all of the observers are right in part, for protoplasm doubt- less assumes all of the above-mentioned forms in different plants and animals and under different conditions. But we must also bear in mind that when we make observations on protoplasm it may be already dead when we examine it — and therefore undoubtedly greatly changed in structure — or else we may view it under conditions which are far from the normal con- ditions under which it usually exists as living matter. Finally, the instru- ment we call the microscope, although seeming to be nearly perfect, may not always give to our eye an exact representation of what is under its lenses. Cells of Various Sizes and Shapes. — Plant cells and animal cells are of very diverse shapes and sizes. There are cells so large that they can easily be seen with the unaided eye; for example, the root hairs of plants and eggs of some animals. On the other hand, cells may be so minute that in the case of the plant cells we call bacteria, several mil- lion could be placed on a dot of this letter i. The forms of cells may be ex- tremely v
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