from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The complex, semifluid, translucent substance that constitutes the living matter of plant and animal cells and manifests the essential life functions of a cell. Composed of proteins, fats, and other molecules suspended in water, it includes the nucleus and cytoplasm.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The entire contents of a cell comprising the nucleus and the cytoplasm. It is a semi-fluid, transparent substance which is the living matter of plant and animal cells.
from the GNU version of the Collaborative International Dictionary of English
- n. The viscid and more or less granular material of vegetable and animal cells, possessed of vital properties by which the processes of nutrition, secretion, and growth go forward; the so-called “ physical basis of life;” the original cell substance, cytoplasm, cytoblastema, bioplasm sarcode, etc.
from The Century Dictionary and Cyclopedia
- n. An albuminoid substance, ordinarily resembling the white of an egg, consisting of carbon, oxygen, nitrogen, and hydrogen in extremely complex and unstable molecular combination, and capable, under proper conditions, of manifesting certain vital phenomena, as spontaneous motion, sensation, assimilation, and reproduction, thus constituting the physical basis of life of all plants and animals; sarcode.
- n. The invisible basis of living substance; the ultimate and true protoplasm as free from all non-living objects. See the extract.
- n. Chemical structure. To chemical examination protoplasm yields large amounts of proteids and of water, as well as some fats, carbohydrates, and mineral substances. Of these the proteids are preëminent in some fundamental phenomena of protoplasm. Whether the ultimate protoplasm is one chemical substance or a mixture of substances is not known. Visible portions of protoplasm are complex and non-homogeneous in most cases and minute contiguous areas give different chemical reactions.
- n. Physical structure. Protoplasm is essentially liquid in many of its active phases, with great differences of viscosity in different areas and in the same area at different times. It often looks like an emulsion and some of its properties S.—68 are comparable with those of colloidal solutions. Assuming electrical charges in protoplasm, such fundamental activities as contraction of muscle and transmission by nerves have found formal explanations.
- n. Deduced biological structure. To explain heredity and some other phenomena of living things, protoplasm has frequently been regarded as made up of units which are generally thought of as ultramicroscopic. Among such units of ultimate protoplasm are the ‘physiological units’ of Herbert Spencer, the ‘gemmules’ of Darwin, the ‘pangens’ of De Vries, the ‘plastidules’ of Haeckel, the ‘biophores’ of Weismann, the ‘micellæ’ of Nägeli, and the ‘plasomes’ of Wiesner. In some cases these units are held to have some of the fundamental attributes of living things. These conceptions afford only formal explanations of certain protoplasmic phenomena.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. the substance of a living cell (including cytoplasm and nucleus)
The term protoplasm is still in use with different meanings as used by different writers.
From this time forth this term protoplasm was applied to the living material found in all cells, and became at once the most important factor in the discussion of biological problems.
This common base is the physical and chemical character of the mixture of substances which we call protoplasm ....
I began with what I called the protoplasm of religion, the primitive ideas and practices which form the psychological basis of the whole growth.
We do not know, it is said, by what means the structureless viscid substance which we call protoplasm can build for itself a solid bone; we do not understand how an amoeba makes its test; no one understands how anything is done unless he can do it himself; and even then he probably does not know how he has done it.
A hundred years ago, when scientists believed cells were full of a mysterious substance they called protoplasm, that was a legitimate scientific question.
The body protoplasm is generally crescentic; there are two chromatin masses, the larger one, the nucleus, on the side of the convexity, the other narrower, more deeply stained situated usually on the edge of the concavity, the centrosome.
To this material he now gave the name protoplasm, choosing a name hitherto given to the cell contents of plant cells.
And we have seen that the essential substance of a cell is a complex chemical compound we call protoplasm, whose elements are identical with chemical substances outside the living world.
 The word protoplasm must not be misunderstood to mean a substance of a definite chemical nature, or of an invariable morphological structure; it is applied to any part of a cell which shows the properties of life, and is therefore only a convenient abbreviation for the phrase "mass of living matter."