Protoplasm

“ We have seen how it is always changing, always taking in food, always giving off waste materials. We have seen, too, that it grows and that it does work, and that in a large mass the cells which compose it share the labour instead of each component cell performing all the vital functions. We have now to consider the work which protoplasm does—in a word, the mechanical effect of the chemical actions just described.
The simplest movement of protoplasm is to be seen by the aid of the microscope in certain vegetable cells, where granules seem always streaming about in different directions. ”

“ Protoplasm, after thus augmenting its mass, has a further power of spontaneous division, whereby the mass of the entire organism whereof such protoplasm forms a part, is augmented and so growth is brought about.
The small particles of protoplasm which constitute "cells" are far indeed from being structureless. Besides the nucleus already mentioned there is a delicate network of threads of a substance called chromatin within it, and another network permeating the fluid of the cell substance, which invest the nucleus often with further complications. ”

“ To their view, we cannot fancy protoplasm as so much matter in a pot, in an ointment-box, any portion of which scooped out in an ear-picker would be so much life-stuff, and, though a part, quite as good as the whole. This seems to be Mr. Huxley’s conception, but it is not theirs. A certain 92measure goes with protoplasm to constitute it an organism to them, and worthy of their attention. They refuse to give consideration to any mere protoplasm-shred that may not have yet ceased, perhaps, to exhibit all sign of contractility under the microscope, and demand a protoplasm-cell. ”

“ Probably it has an exceedingly complex structure, but our microscopes and technique are still too imperfect to show more than traces of it. Says Hertwig: "Protoplasm is not a single chemical substance, however complicated, but a mixture of many substances, which we must picture to ourselves as finest particles united in a wonderfully complicated structure." Truly protoplasm is, to borrow Mephistopheles' expression concerning blood, a "quite peculiar juice." And the complexity of the nucleus is far more evident than that of the protoplasm. Is protoplasm itself the result of a long development? ”

“ We have seen that protoplasm has a very complicated structure, and that its normal condition is one of change. This being so, it obviously cannot exist in large masses, for if it did the change would be sure to be uneven in different parts from its very complexity; and the centre of the lump would either be starved or poisoned by the products of its own life. To avoid this, the mass is divided up into a vast number of small units each complete in itself, in communication more or less direct with its neighbours, and all equally accessible to fluids which both feed and cleanse them. ”

“ In the different propositions I have quoted, we [Pg 36] have to deal with what is merely a fallacy in rhetorical disguise. For, from the premiss that the chromatin has the power of impressing specific character upon the protoplasm of the cell, it by no means follows that two cells, distinguishable by the nature of their plasma-products, must therefore contain different kinds of protoplasm. There are other possibilities to be reckoned with. ”

“ It is done every day by plants which make protoplasm out of inorganic elements, and by the lowest forms of life which live and multiply in chemical solutions. It is done also in the life-history of all individuals whose primitive cell or ovum makes thousands or millions of other cells, each containing within its enclosing membrane as much protoplasm as there was in the unit from which they started. But in all these instances there was the living principle to start with, existing in the primitive speck of protoplasm, from which the rest were developed. ”

“ So far as yet discovered, all protoplasm, whether vegetable or animal, is derived from pre-existing protoplasm. The spontaneous production of living matter from non-living materials has never been satisfactorily proved. The particular kind of protoplasm which we are about to consider—viz., the human germ—is the combined derivative of certain glands which exist in separate adult human beings who represent the opposite sexual polarities belonging to all except the lowest vegetable and animal types. ”

“ The evidence points to a common and universal law that continued life is an attribute of an especially endowed protoplasm, termed germ plasm, which forms the material basis of the reproductive cells.
The history of single Protozoa, if taken superficially, seems to point to the fact that the protoplasm of these cells does not die a natural death, but continues to live in successive generations of similar individuals. The individual cell appears to be entirely self-sufficient ”

“ But the further researches of physiologists and the improvements in the technique of the microscope proved that protoplasm does not exist independently in nature; because living cells are always a combination of protoplasm and a nucleus. If the nucleus is extracted from a radiolarium, the latter mortifies, and the protoplasm also dies; if an amœba is severed in such a manner that one part contains nucleus and protoplasm and the other protoplasm alone, it will be found that the latter part mortifies and dies, while the first part continues to live. ”

“ One of them refers to the structure of protoplasm as revealed by the microscope. Throughout the whole of the living kingdom, from the bacteria studied by Kunstler and Busquet to the most complicated protozoa, protoplasmic matter presents the same constitution, and in consequence, this structure of the protoplasm must be considered as one of its distinctive characters. It is not homogeneous; it is not the last term of the visible organization: it is itself organized. Experiment shows that it does not resist breaking up or crushing. Mutilations cause it to lose its properties. ”

“ Fig. 8.—Cross-Section of Petiole of Begonia-Leaf, shows Crystals in the Cells (copied from Prantl.)
protoplasm is the simplest form of living matter with which we are acquainted, is the living element of every living cell. One of the most characteristic phenomena of life is independent motion, and protoplasm more frequently reveals itself by moving. Such is the case in the cells we are now considering. In 1869 Professor Huxley set the thinking world all agog by describing, in a passage of wonderful accuracy and beauty, what he could see of moving protoplasm in the hair of a stinging nettle. ”

“ As in this case the protoplasm is but a fragment, and as it is removed from the influence of the parent-cell, this differentiating process can scarcely be regarded as anything more than the effect of physico-chemical actions: a conclusion which is supported by the statement of Sachs that "not only every vacuole in a solid protoplasmic body, but also every thread of protoplasm which penetrates the sap-cavity, and finally the inner side of the protoplasm-sac which encloses the sap-cavity, is also bounded by a skin" (p. 42) . ”

“ The new science of cytology has made us aware that the division of cells is not a passive or a simple process, but is extremely active, complex and varied. Living protoplasm is in motion, and the discovery that cell walls are not hermetically closed, but are perforated by delicate protoplasmic strands, lends strength to the belief of some biologists that protoplasm circulates, not only inside the individual cells, but through the entire organism. Conjugation may signify that such a circulation extends also throughout the species. ”

“ Now this wonderful substance, chemically and physically the same in the highest animal and in the lowest plant, has been all along the puzzle of the biologist. How is it that in man protoplasm works out human structure; in fowl, fowl structure, &c. &c., while the protoplasm itself appears to be everywhere the same? To Professor Yaeger belongs the great merit of having shown us that the protoplasms of the various species of plants and animals are not the same; that each of them contains, moreover, imbedded in its molecules, odorant substances peculiar to the one species and not to the other. ”

“ To look at living cells through a microscope would almost surely be a disappointment at first, for protoplasm is so transparent that not much of its form can be seen on direct inspection. Fortunately for our knowledge of how cells are made up, protoplasm that has been properly killed and preserved takes stain very well, and different chemical substances in the protoplasm stain differently. Thus features that could not be made out at all in the living cells become clearly visible after killing and staining. ”

“ Its true nature and composition are unknown, because any attempt to analyze it kills it, and dead protoplasm is essentially different from living protoplasm. It is known, however, to be a highly complex substance and to undergo chemical change readily. It appears to be the only kind of matter with which life is ever associated, and for this reason protoplasm is called the physical basis of life. Its organization into separate bits, or cells, is necessary to the life activities that take place within it. ”

“ The word protoplasm has almost as wide a generality as the word animal, and is often used in forgetfulness of its specific values: the protoplasm of a nerve-cell is not the same as that of a blood-cell, a muscle-cell, or a connective-tissue cell, any more than a bee is a butterfly, or a prawn a lobster. No sooner has the specific character been acquired, no sooner is one organite formed by differentiation, than there is an absolute barrier against any transformation of it into any other kind of organite. ”

“ Now, of all substances, protoplasm seems to consist of the largest number of components, and to have them arranged in the most complicated way known; though ‘known’ is really not the right word to use in this connection. The reason why we do not know what life is, is that we cannot find out in what way the constituent compounds in the protoplasmic structure are combined. Directly we try to analyze protoplasm, it dies ”

“ By careful focusing it is easy to show that the protoplasm is confined to a thin layer lining the wall, the central cavity of the tube being filled with cell sap. In the protoplasm are numerous elongated chloroplasts (cl.) . and a larger or smaller number of small, shining, globular bodies (ol.) . These latter are drops of oil, and, when the filaments are injured, sometimes run together, and form drops of large size. No nucleus can be seen in the living plant, but by treatment with chromic acid and staining, numerous very small nuclei may be demonstrated. ”

“ The ultimate step, as we must suppose, is the formation of living protoplasm out of these non-living proteids. A cardinal fact is that proteids admit of multitudinous transformations; and it seems not improbable that in protoplasm various isomeric proteids are mingled. If so, we must conclude that protoplasm admits of almost infinite variations in nature. Of course pari passu with this dual process—augmentation of protoplasm and accompanying production of carbo-hydrates—there goes extension of plant-structure and plant-life. ”

“ In this later treatise ('Botanische Zeitung,' 1846) , in which he proves that the well-known movements in the interior of cells are made not by the watery cell-sap but by the protoplasm, he states (p. 75) that it is the protoplasm which produces the nucleus, that the organisation of the nucleus ushers in the formation of the new cell, and that contrary to Schleiden's theory the protoplasm completely envelopes the nucleus, which always occupies the centre of very young cells, as is the case especially in the endosperm-cells observed by Schleiden. ”

“ While the protoplasm of the biologist is a substance which is more or less opaque or visible, the protoplasm now conceived of as the material of the whole creation in its first state, when development is to begin, must, on the contrary, be altogether homogeneous and invisible. But none the less is it entitled to the name of protoplasm; nay, it alone must be justly entitled to that name, for it is the first of created things, and, being the product of an Almighty Being, it must be altogether plastic in His hands. It can have no constitution of its own derived from itself ”

“ What, then, can be the nature of protoplasm? Struck by its homogeneity, the identity of the elements that compose it with those that form albuminoid substances, it has been taken for a mere chemical compound, and it has been boldly asked if it is not possible to produce it artificially; if man has not power to relight the torch of Prometheus and create life at will. ”

“ A still more important point in connection with this protoplasm question consists in the fact that as we go backward to the beginnings of life, both in animals and plants, we seem to approach nearer and nearer to an identity of substance which baffles the microscope with all its powers of discernment. Every animal and every plant begins existence as a mere speck of this living jelly. The germ of each is a protoplasm particle, which, whatever traces of structure it may exhibit, is practically unrecognizable as being definitely animal or plant in respect of its nature. ”