Nucleus (biology)

“ The Nucleus.—The nucleus has been demonstrated in all plants with the exception of the Cyanophyceae and Bacteria, and even here structures have been observed which resemble nuclei in some of their characteristics. The nucleus is regarded as a controlling centre of cell-activity, upon which the growth and development of the cell in large measure depends, and as the agent by which the transmission of specific qualities from one generation to another is brought about. ”

“ The Nucleus.—Every cell capable of living, growing, and multiplying, possesses a nucleus of constitution very analogous to the cellular mass which surrounds it. The anatomical elements in which no nucleus is found, such as the red globules of blood in adult mammals, are bodies which are [Pg 164] certain, sooner or later, to disappear. There is therefore no real cell without a nucleus, any more than there is a nucleus without a cell. ”

“ The first stage in the history of these fiery particles is the formation among them, in some unaccountable way, of [Pg 4] nuclei, or centres of aggregation, like the bright points that are now visible in some of the nebulæ of the heavens. As soon as these centres are formed, gravity, one of the original principles of matter, begins to act, and the atoms in all the neighbouring parts of space are attracted towards the nucleus and heaped upon it. ”

“ Up to the point we have reached, then, we see what the new view of Matter is. Every atom of matter, of whatever kind throughout the whole universe, is built up of electrons in conjunction with a nucleus. ”

“ Here then within the territory of a single cell we have differentiation. If now in these unicellular organisms we study both the protoplasm and the nucleus, we learn that most of these modifications which are so conspicuous upon microscopic observation are due to changes in the protoplasm. It is the protoplasm which acquires a new structure. In the nucleus, on the contrary, we find perhaps a change of form, minor details of arrangement by which one sort of nucleus, or one stage of the nucleus, can be distinguished from another, but always the nucleus consists of the same fundamental constants. ”

“ Nevertheless, it is a fact, and a comprehension of it will enable you to adjust yourself to other facts, one of which is that the Infinite Intelligent Energy compels each and every atom to assume its orderly relation to all other atoms. Further, that indeed, atoms are embryotic universes, each atom containing within itself all the properties which anywhere exist, and any one atom may [Pg 81] form the nucleus about which other atoms may congregate, until a world is in process of formation. ”

“ To make room for these we have to remember that the atomic nucleus has remained entirely undefined and beyond our problem; so that what may occur, say when two molecules come into close relations, is outside physical science—not, however, altogether outside, for we know that when the vital nexus in any portion of matter is dissolved, the atoms will remain, in their number, and their atmospheres, and all inorganic relations, as they were before vitality supervened. ”

“ Each of the ninety-two elements which we believe constitute the ninety-two different forms of simple matter has an atom with its own peculiar type of nucleus, which nucleus differs from those of the others only in the amount of positive electricity it contains. ”

“ Thus in the class Infusoria two nuclei are found in each individual; a macronucleus which is somatic in function, that is to say, which regulates the metabolism and vital processes of the body generally, and the micronucleus, which is generative in function, that is to say, which remains in reserve during the ordinary, “vegetative” life of the organism and becomes active during the act of syngamy, after which the effete macronucleus is absorbed or cast out and a new somatic nucleus is formed from portions of the micronuclei which have undergone fusion in the sexual act. ”

“ If that was the fundamental and only really essential form, the Darwinian primitive and initial type of all terrestrial life must have been a similar drop of living matter with a solid central nucleus, a nucleated individual cell. ”

“ The nucleus represents the most vital part of the cell protoplasm, and has a more granular appearance than the latter. The nucleolus is a minute solid spot in a nucleus, appearing to be more highly refractive. ”

“ But it is the nucleus which directs and determines all definite growth, movement, secretion, and reproduction. The simple protoplasm, deprived of its nucleus, cannot form a new nucleus—in fact, can do very little but exhibit irritability. I am inclined to agree with those who hold that there is not sufficient evidence that any organism exists at the present time which has not both protoplasm and nucleus—in fact, [120] that the simplest form of life at present existing is a highly complicated structure—a nucleated cell. ”

“ For example, a molecule of water consists of two atoms of hydrogen and one of oxygen, which can be separated from each other by chemical methods. An atom, in its turn, is found to be a sort of solar system, with a sun and planets; the empty regions between the Sun and the planets fill up vastly more space than they do, so that much the greater part of the volume that seems to us to be filled by a solid body is really unoccupied. In the solar system that constitutes an atom, the planets are called “electrons” and the Sun is called the “nucleus.” ”

“ Nucleolus: the small portion of matter in the nucleus most readily affected by staining fluids.
Nucleus: a well-defined, differentiated, round or oval body imbedded in the cell contents.
Nude -us: naked: a surface devoid of hair, scales or other vestiture. ”

“ To do that I have had to get at the center force of the ion, the spirit, life, or what you will. You understand the ovum, the first form of life—the germ in the egg sac?"
"' "Yes, to a certain point; it is the meaning of all life, the nucleus that splits and becomes two, four, eight, protoplasmic cells, called blastomeres, and each one containing a nucleus like the original. They multiply by division; they are the secret of all life—and the mystery." ”

“ We may consider a plant as a body; then the phytons of which it is composed are particles. A phyton may be considered as a body, then the cells are considered as particles; in turn, the cell may be considered as a body, then its blasts may be considered as particles. Then a blast as the nucleus may be the body whose particles are molecules, and the molecule as a body has atoms for its particles. Thus there is a hierarchy of bodies and of particles in the plant realm in which the bodies have form while the particles have space. ”

“ Of the whole cell, the nucleus is to him, as it was to Schleiden, Schwann, and others, the most important element. And this is the view to which I, who have little business to speak, wish success. This universe is not an accidental cavity, in which an accidental dust has been accidentally swept into heaps for the accidental evolution of the majestic spectacle of organic and inorganic life. That majestic spectacle is a spectacle as plainly for the eye of reason as any diagram of the mathematician. ”

“ We know that growth and development in animals and plants are determined by definite although complicated series of catenary chemical reactions, which result in the synthesis of a DEFINITE compound or group of compounds, namely, NUCLEINS.
The nucleins have the peculiarity of acting as ferments or enzymes for their own synthesis. Thus a given type of nucleus will continue to synthesise other nuclein of its own kind. This determines the continuity of a species; since each species has, probably, its own specific nuclein or nuclear material. ”

“ As we saw in Chapter I, an atom is a kind of solar system, consisting of a nucleus which has electrons revolving round it. We shall see later that it is the nature of the nucleus that characterizes an element, and that two atoms of the same element may differ as to the number of their electrons and the shapes of their orbits. ”

“ Before undertaking a further description of the nucleus itself, we shall be helped to an understanding of its function if we trace briefly the history of the cells which make up our body. At the beginning, as we probably all know, we start life as a single cell. ”

“ It may further be added, as a general truth applicable to nucleated cells, that the nucleus rarely undergoes any considerable modification, the structures characteristic of the tissues being formed at the expense of the more super ficial protoplasm of the cells ; and that, when nucleated cells divide, the division of the nucleus, as a rule, precedes that of the whole cell. ”

“ Are the smallest particles of living matter which still exhibit all its func­tions of the order of magnitude of molecules and atoms, or are they of a different order? The first step toward obtaining an answer to this ques­tion was taken by Moritz Nussbaum,139 who found that if an infusorian be divided into two pieces, one with and one without a nucleus, only the piece with a nucleus will continue to live and perform all the func­tions of self-preserva­tion and development which are characteristic of living organisms. ”

“ Thus the nucleus was restored to the important position which Schwann and Schleiden had given it, but with greatly altered significance. Instead of being a structure generated de novo from non-cellular substance, and disappearing as soon as its function of cell-formation was accomplished, the nucleus was now known as the central and permanent feature of every cell, indestructible while the cell lives, itself the division-product of a pre-existing nucleus, and the parent, by division of its substance, of other generations of nuclei. ”

“ If the growth period of the nucleus is very long, the greater part of the protoplasm may be taken into the nucleus, as in those cleavage cells in which the nuclear volume is about three times as great as that of the protoplasm outside of the nucleus; if the growth period of the nucleus is short, the nucleus remains correspondingly small. ”

“ The nucleus is the physical basis of all the heritages of an organism, from the simplest to the most complex. The nuclear threads may, therefore, very appropriately be termed the hereditary threads, or, collectively, the hereditary mass; and the physiological units in them the hereditary units. The nucleus is [42] of fundamental importance in the reproduction or multiplication of both unicellular and multicellular animals and plants.
In unicellular creatures multiplication may take place by fission and by conjugation. ”

“ We can imagine the atomic nucleus as composed of a large number of primates of differing species, and perhaps with many primates of the same species, the whole association being such as to favour stability. An example of such an association is afforded by the association of a positive nucleus with negative electrons to obtain a neutral atom. ”

“ One of the German chemists is convinced that the nuclein in the nucleus of the cell is not a very complicated compound. Under such conditions it is not a matter of surprise that the physiological chemist should be constantly dreaming that he may at some time produce living matter in the laboratory. To the ordinary mind it scarcely seems possible. We are so [Pg 162] entirely sure that life is not amenable to physics or chemistry that we can hardly conceive of the possibility of its originating out of matter in the test tube. ”

“ Now we know something about the names of the important kinds of atoms and can take up again the question of how they are formed by protons and electrons. No matter what kind of atom we are dealing with we always have a nucleus or center and some electrons playing around that nucleus like tiny planets. The only differences between one kind of atom and any other kind are differences in the nucleus and differences in the number and arrangement of the planetary electrons which are playing about the nucleus. ”

“ The splendid increase of microscopical lens power during the past decade has not only enabled us to see that there is complexity and structure in both the animal and vegetable cell, which bisects by an elaborate process; but even the minute nucleus of the minutest organisms, often not more than one tenth part of the infinitesimal body itself, is now proved to undergo profound structural changes, which precede all the great cyclic changes of the organism as a whole. The nucleus is the centre, in fact, of all the higher activities of the least and lowest infusoria ”

“ It is by reason of the same tendency to confluence or aggregation of particles that the ordinary nucleus is itself formed, until the imposition of a new force leads to its disruption.
Apart from that invisible or ultra-microscopic heterogeneity which is inseparable from our notion of a “colloid,” there is a visible heterogeneity of structure within both the nucleus and the outer protoplasm. ”

“ We know, for example, that the nucleus often exists in the cell, though an acid may be needed to make it visible. We also know that cells which during life are quite free from visible granules are distinctly granulated after death, even without external chemical action. ”

“ The nucleus is looked upon by the majority of cytologists as the formative center of the cell in a chemical, and also, consequently, in a morphological, sense. Active exchanges of material take place between the nucleus and the protoplasm during the nutritive processes of the cell. ”

“ The nucleus plays the same part in the life of the single celled organisms as it does in the cells of the Metazoa and Metaphyta. It appears to influence in a certain manner all, or at least most, of the processes of life, such as motility, regeneration, growth, and generally also digestion. Its principal influence, however, is exercised in the propagation of the cells, as this is always brought about by the nucleus. ”