Dry cell

“ Water should not be allowed to come in contact with the paper covers of the cells because they form the insulation, hence, when moist,61 current will leak across from one cell to another, resulting in running down the battery. 4. Dry cells will deteriorate when not in use, making it necessary to renew them about every sixty days. The reason dry cells deteriorate is because the moisture evaporates. ”

“ Though it is extremely difficult to separate the cell wall of bacteria from the cell contents, in the light of our present knowledge it can be stated that the cell walls are composed of a carbohydrate body closely related to cellulose, though not true cellulose, probably in close combination with chitin.
Of the organic constituents of the cell contents the most abundant are various proteins which ordinarily make up about one-half of the dry weight of the entire cell. ”

“ The naked cells which have been alluded to live in water, and call therefore for no differentiation in connexion with this necessity; but those which are surrounded by a cell-wall always develop within themselves a vacuole or cavity which occupies the greater part of their interior, and the hydrostatic pressure of whose contents keeps the protoplasm in contact with the membrane, setting up a condition of turgidity. ”

“ The yeast-cell with its bud is a simple example of a principle which we shall find to be very important. Our whole treatment of cell-form in relation to surface-tension depends on the fact (which Errera was the first to point out, or to give clear expression to) that the incipient cell-wall retains with but little impairment the properties of a liquid film281, and that the growing cell, in spite of the membrane by which it has already begun to be surrounded, behaves very much like a fluid drop. ”

“ The cells of which they are built up are comparatively large, and, like almost all vegetable cells, are each inclosed in a wall of cellulose. The cellulose is perfectly transparent, and if the microscope, even with a low power, be brought to bear on one of these cells, a portion of its protoplasm may be seen in active rotation, flowing up one side of the long, tubular cell and down the other, and sweeping on with it such more solid particles as may become enveloped in its current. ”

“ Woody and other substances are deposited in every cell in different quantities according to their kinds and the accompanying circumstances, and clothe their walls; the unequal thickness of the layer so deposited appears according to Hugo von Mohl to have given rise to the supposition of perforated cells; that is, the parts of the cell-wall that remain transparent appear under the microscope as pores. Every cell may be regarded as a body which prepares juices in its interior ”

“ On its surface is formed a perfect membrane, which is everywhere free on its outer face. There are two processes in the formation of a cell; the first is the isolation or individualising of a part of the contents of the mother-cell, the second the formation of a membrane round the individualised portion.' He then proceeds to show that the cell-wall is formed by the separation of non-nitrogenous molecules from the nitrogenous mucilage (proto-plasm) . These sentences contain all that is general and essential in vegetative cell-formation. ”

“ From the adjacent cells distinct outgrowths are being emitted, where the surface tension has been weakened: just as the glass-blower warms and softens a small part of his tube to blow out the softened area into a bubble or diverticulum; and in our Mesocarpus cells (besides a certain amount of potassium rendered visible over the boundary which {290} separates the green protoplasm from the cell-sap) , there is a very large accumulation precisely at the point where the tension of the originally cylindrical cell is weakening to produce the bulge. ”

“ Now, it must have become evident from our previous chapters, that the further development of all other organisms out of such a cell presents no difficulty, for every animal and every plant, in the beginning of its individual life, is a simple cell. Man, as well as every other animal, is at first nothing but a simple egg-cell, a single lump of mucus, containing a kernel (p. 297, Fig. 5) .
In the same way as the kernel of the organic cell arose in the interior or central mass of the originally homogeneous lump of plasma, by separation, so, too, the first cell-membrane was formed on its surface. ”

“ But some cells, especially young ones, are entirely without the enveloping membrane, or stiff wall. Hence we now generally describe the cell as a living, viscous particle of protoplasm, enclosing a firmer nucleus in its albuminoid body. There may be an enclosing membrane, as there actually is in the case of most of the plants; but it may be wholly lacking, as is the case with most of the animals. There is no membrane at all in the first stage. The young cells are usually round, but they vary much in shape later on. ”

“ If you press some of the
cells lightly they will burst, the soft inside part will flow out and leave the empty sac just the shape of the cell except where it is torn. This shows that the outside is much stronger and tougher than the inside. Chemists have found that this wall of the cell is made exactly the same as the tough cells of wood—it is called cellulose.
The light-colored jelly inside the sac has a long name of its own—protoplasm—which means first form or mould, because this seems to be the first form of all life. The green and the red colored grains are called chlorophyll. ”

“ In this case the original cell wall remains as part of the wall of the daughter cells. Fission is the commonest form of cell multiplication throughout the vegetable kingdom.
The second form of cell division or internal cell division is shown at C. Here the protoplasm and nucleus repeatedly divide until a number of small cells are formed within the old one. These develop cell walls, and escape by the breaking of the old cell wall, which is left behind, and takes no part in the process. The cells thus formed are sometimes provided with two cilia, and are capable of active movement. ”

“ Most cells are inclosed by a cell-wall, and contain a watery cell-sap, and a mucilaginous semi-fluid substance called protoplasm, composed of different organic constituents; among these nitrogenous or albuminous matter is always present, and in the largest proportion. In some plants the protoplasm is not at first inclosed by cell-walls, but it is sooner or later enclosed in a more or less elastic membrane. No cell can exist in a living state or grow unless it contains protoplasm, which is therefore the basis of all vegetable life. ”

“ The individuals—each known as a frustule—assume very various forms and may be unicellular or multicellular, but present no differentiation; many similar cells may be connected in chains, embedded in mucilaginous masses, or attached to mucilaginous stalks. The cells are bilateral or centric, often asymmetrical, slightly dorsiventral and have no cilia; those living in the free condition have the power of sliding upon a firm substratum. The cell contains 1 cell-nucleus and 1–2 plate-shaped or several disc-shaped chromatophores. ”

“ The cells of which all plants and animals consist increase in numbers by the division of [Pg 10] each cell into two cells through the formation of a division wall across the cell. The new cells divide and the plant or animal continues to grow. The same cell division occurs in the bacteria but since the bacteria are single celled, division of the cells means an increase in numbers rather than growth as in the higher forms of life. ”

“ With regard to the former, we have seen that in the single cells, constituting unicellular organisms, there is always a bounding membrane of denser texture than the rest of the protoplasm. As the cell develops its capabilities, we have a shell or case of non-living matter secreted around it, with apertures for communication with the outside world, and increasingly effective protection is provided as protoplasm, whether in the single cell or the body, leaves the water, and has to face the inclemencies of terrestrial life. ”

“ In the simplest plants, consisting of a single cell, no differentiation of the parts can be perceived. Food is taken in on all sides alike, and is worked up in the whole plasma of the cell and applied to the growth of the cell-body, to the multiplication of cells by division, or is stored up as reserve food. This is possible because the cell either lives continuously in a uniform element, water, or, if it dries up, simply suspends its life while the dryness continues. ”

“ As the cell increases in size as a result of growth, it elongates in one direction, and finally a new cell wall is formed, dividing the so-called mother-cell into two, equal-sized daughter-cells. This process of cell division, known as fission, is continued until growth ceases and is especially characteristic of bacteria. ”

“ 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. ”

“ In some free-swimming cells, such as the individual cells known as "Flagellata," the reproductive cells of the lower Plants, or the male cells ("spermatozoa") of Plants as high as Ferns, and even of the Highest Animals, there is an extension of the cell into one or more elongated lash-like processes, termed "flagella," which, by beating the water in a reciprocating or a spiral rhythm, cause the cell to travel through it; or, if the cell be attached, they produce currents in the water that bring food particles to the surface of the cell for ingestion. ”

“ In every real cell there is, besides protoplasm, and while still alive and independent, a second important constituent, the cellular germ, so called (nucleus or cytoblast) ; but even this germ consists of an albuminous chemical compound which is closely related to protoplasm, and was orginally produced from it by an exceedingly slight chemical alteration. The germ is usually a smaller and firmer formation within the protoplasm of the cell. ”

“ This is done by pulsation of the vacuole, which ultimately bursts, passing fluid waste to the outside. Solid wastes are passed out of the cell in somewhat the same manner. No breathing organs are seen, because osmosis of oxygen and carbon dioxide may take place anywhere through the cell membrane. The nucleus of the cell is not easily visible in living specimens. ”

“ During the time protoplasm was being observed the cell had likewise come under close scrutiny, and naturalists had now an extensive collection of facts upon which to found a theory. It has been shown that many animal cells have no cell-wall, and the final conclusion was inevitable that the essential part of a cell is the semifluid living substance that resides within the cavity when a cell-wall is present. Moreover, when the cell-wall is absent, the protoplasm is the "cell." ”

“ As, moreover, the first thing which a cell does when it grows is to divide, the whole proceeding looks rather futile. But ready-made protoplasm of an assimilable shape is rare, and it is not often that a cell, unless it be a plant or a parasite, finds itself in a substance which can be handed straight to the nucleus without further elaboration. Usually the cell has to discharge from itself a reagent, which will develop the right chemical qualities in the matter it wants to absorb. This substance is known as an enzyme, or ferment. ”

“ These crystals occur in special storage cells—crystal cells (Plate 65, Fig. 6) —which usually form a completely enveloping layer around the bast fibres. These cells are usually the smallest cells of the plant in which they occur, and with but few exceptions each cell contains but a single crystal.
The epidermal cells of senna leaves and the epidermal cells of mustard are filled with mucilage; the walls even consist of mucilage. Such cells are always diagnostic in powders. ”

“ This body is called the nucleus of the cell, and the small one within it, the nucleolus.
The membrane surrounding the cell is known as the cell wall, and in young plant cells is always composed of cellulose.
The granular substance lining the cell wall (Fig. 1, pr.) is called “protoplasm,” and with the nucleus constitutes the living part of the cell. If sufficiently magnified, the granules within the protoplasm will be seen to be in active streaming motion. This movement, which is very evident here, is not often so conspicuous, but still may often be detected without difficulty. ”

“ The mother-cell simply splits into two daughter-cells and these form a generation of four cells, while later generations, consisting of perhaps one million cells, can in fifteen or twenty minutes produce two million bacteria. But conditions must be favorable for this active growth, ample food stuffs, free from other bacteria, together with moisture and reasonable warmth are most essential. ”

“ Cells were then recognized as the ultimate units of organic structure, which were variously modified to adapt them to diverse special purposes. This cell theory of organized structure was generally adopted, and cells were defined as closed membranes or sacs, containing a more or less fluid substance which served to nourish them. The cells were looked upon as independent units, which multiplied by a process of budding or by self-division, and a new factor was introduced in the discussion of the mooted question as to what constitutes the individual in plants. ”