A dam is a bank or construction of stone, earth, or wood etc across a stream or river for the purpose of keeping back the current to give it increased head, for holding back supplies of water, for floodinglands, for rendering the stream above the dam navigable by increased depth, and for generating electricity. Its material and construction will depend on its situation and the amount of pressure it has to bear. For streams which are broad and deep strong materials are required, usually stone masonry bound in hydraulic cement and a strong framework of metal or timber. The common forms of a dam are either a straight line crossing the stream transversely, or one or two straight lines traversing it diagonally, or an arc with its convex side towards the current. Research Dam
Glue is an adhesive substance made by boilinganimalhides, hooves or bones. Glue consists of gelatine and chondrin, the proportions defining the adhesive qualities of the glue. Glue made from skins is superior to that made from bones, and the best glue is called 'Scotch glue'.
During the Victorian period large quantities of glue were produced from the skins of sheep, calves, cows, hares, dogs, cats, etc, from the refuse of tanneries and tawing works, from old gloves, from sinews, tendons, and other offal of animal origin.
By a process of cleaning and boiling the albuminoid elements of the animal matter are changed into gelatine. This in a soft jelly-like state constitutes size; dried into hard, brittle, glassy cakes, which before use must be melted in hot water, it formed the common glue used by joiners, etc during the Victorian period. When a solution is mixed with acetic or nitric acid it remains liquid, but still retains its power of cementing; in this state it is called liquid glue. Marine Glue is a cement made by dissolving india-rubber in oil of turpentine or coal-naphtha, to which an equal quantity of shellac is added. Research Glue
The bee is a four winged stinging insect of the order Hymenoptera. Bees form the super-family Apoidea of the sub-order Apocrita.
The most important member of the family is the common hive or honey bee (Apis mellifica). It belongs to the warmer parts of the Eastern Hemisphere, but is now naturalized in the Western. A hive commonly consists of one mother or queen, from 600 to 800 males or drones, and from 15,000 to 20,000 working bees, formerly termed neuters, but now known to be imperfectly-developed females. The last-mentioned, the smallest, have twelve joints to their antennae, and six abdominal rings, and are provided with a sting; there is, on the outside of the hind-legs, a smooth hollow, edged with hairs, called the basket, in which the kneaded pollen or bee-bread, the food of the larvae, is stored for transit.
The queen has the same characteristics, but is of larger size, especially in the abdomen; she has also a sting. The males, or drones, differ from both the preceding by having thirteen joints to the antennae; a rounded head, with larger eyes, elongated and united at the summit; and no stings. According to Huber the working-bees are themselves divisible into two classes: one, the cirieres, devoted to the collection of provisions, etc; the other, smaller and more delicate, employed exclusively within the hive in rearing the young.
The mouth of the bee is adapted for both masticatory and suctorial purposes, the honey being conveyed thence to the anterior stomach or crop, communicating with a second stomach in which alone a digestive process can be traced. The queen, whose sole office is to propagate the species, has two large ovaries, consisting of a great number of small cavities, each containing sixteen or seventeen eggs. The inferior half-circles, except the first and last, on the abdomen of working-bees, have each on their inner surface two cavities, where the wax, secreted by the bee from its saccharine food, is formed in layers, and comes out from between the abdominal rings.
Respiration takes place by means of air-tubes which branch out to all parts of the body, the bee being exceedingly sensitive to an impure atmosphere. Of the organs of sense the most important are the antennae, deprivation of these resulting in a species of derangement. The majority of entomologists regard their function as in the first place auditory, but they are exceedingly ssensitive to tactual impressions, and are apparently the principal means of mutual communication.
Bees undergo perfect metamorphosis, the young appearing first as larvae, then changing to pupae, from which the imagosor perfect insects spring. Whether the offspring are to be female or male is said to be dependent upon the contact or absence of contact of the egg with the impregnating fluid received from the male and stored in a special sac communicating with the oviduct, unfertilized eggs producing males. The further question whether the offspring shall be queens or workers is resolved by the influence of environment upon function. The enlargement of a cell to the size of a royal chamber and the nourishment of its inmate with a special kind of food appear to be sufficient to transform an ordinary working-bee larva into a fully-developed female or queen-bee.
The season of fecundation occurs about the beginning of summer, and the laying begins immediately afterwards, and continues until autumn; in the spring as many as 12,000 eggs may be laid in twenty-four days. Those laid at the commencement of fine weather all belong to the working sort, and hatch at the end of four days. The larvae acquire their perfect state in about twelve days, and the cells are then immediately fitted up for the reception of new eggs. The eggs for producing males are laid two months later, and those for the females immediately afterwards. This succession of generations forms so many distinct communities, which, when increased beyond a certain degree, leave the parent hive to found a new colony elsewhere. Thus three or four swarms sometimes leave a hive in a season. A good swarm is said to weigh at least three kilograms. Besides the common bee (Apis mellifica) there are the Apis fasciata, domesticated in Egypt, the Apis Ugustica, or Ligurian bee of Italy and Greece, introduced into England, etc.
The humble-bees, or bumble-bees, of which about forty species are found in Britain and over sixty in North America, belong to the genus Bombus, which is almost worldwide in its distribution. Of these species solitary females which have survived the winter commence constructing small nests when the weather begins to be warm enough; some of them going deep into the earth in dry banks, others preferring heaps of stone or gravel, and others choosing always some bed of dry moss. In the nest the bee collects a mass of pollen and in this lays some eggs. The cells in these nests are not the work of the old bee, but are formed by the young insects similarly to the cocoons of silk-worms; and when the perfect insect is released from them by the old bee, which gnaws off their tops, they are employed as honey-cups.
The humble-bees, however, do not store honey for the winter, those which survive until the cold weather leaving the nest and penetrating the earth, or taking up some other sheltered position, and remaining there until the spring. The first brood consists of workers, and successive broods are produced during the summer. The experiment of domesticating different kinds of wild bees has been tried with no satisfactory results. Some bees, from their manner of nesting, are known as 'mason bees,' 'carpenter bees,' and 'upholsterer bees.' Some of these bees (genus Osmia) cement particles of sand or gravel together with a viscid substance in forming their nests; others make burrows in wood. The leaf-cutter or upholsterer bee (genus Megachile) lines its burrow with bits of leaf cut out in regular shapes. Research Bee
The Bengal quine or Bel or Belgae (Aegle marmelos) is an Indian tree, the fruit of which is not unlike an orange and is slightly aperient. A perfume and yellow dye are obtained from the rind, and a cement from the mucus of the seed. Research Bengal Quince
Epithelium is an anatomical term for a basic type of bodily tissue. It comprises the external surface of the skin, the internal surfaces of the digestive, respiratory and urogenital systems, the closed serous cavities, the inner coats of the vessels, the acini and ducts of the secreting and excreting glands, the ventricles of the brain and the central canal of the spinal cord. The constituent cells of an epithelium are always closely packed together and the intercellular substance is reduced to a minimum. The cells comprising an epithelium are arranged in one (simple epithelium) or more (stratified epithelium and transitional epithelium) layers, usually supported on a basementmembrane and united together by a cement-like substance which is chemically similar to the matrix or ground-substance of the connective tissues.
The epithelium serves various purposes. The epithelium of the skin (known as the epidermis) serves primarily to protect the underlying tissue (the true skin, nerves and vessels which it contains). Th epithelium of the salivary glands, the pancreas, the gastric glands and the glands of the small intestine are comprised of cells which prepare the digestive juices. The cells comprising the epithelium of the intestinal villi are concerned with the absorption of the products of digestion. The cells of the epitheliums of the serous cavities provide a smooth, moist surface. Rather unusually in the body, the epithelium is devoid of a blood supply Research Epithelium
When any portion of body tissue has been destroyed by disease or violence, the adjacent tissues at once set to work to repair the gap. Clearly their task will depend on the extent of the gap and the presence of any factors which hinder normal tissue activity. When a clean surgical incision has been made and the edges sewn closely together the gap to be bridged is very thin. On the other hand, if there has been an abscess and a large area of tissue has been dissolved away, the problem is very much greater. There are many factors which infuence the rate of the body's power of healing. Where a gap has been left in the tissues, the 'raw' surfaces are covered with blood clot and any intervening cavity may in fact be filled with blood. From the ends of the capillaries which have been cut on either side, cells grow rapidly into this haematoma (a collecion of blood in the tissues) and form granulation tissue, which is thus a mass of tiny little capillary buds with fibrous tissue cells.
As the days go by, the very rich blood supply enables fibrous tissue to grow rapidly and become more dense, and finally to cement the gap. Weeks later the blood vessels die off and firm fibrous tissue (scartissue) remains. This becomes slowly tighter and tighter. This process we know as contraction, so that what may appear to be quite a large scar shrinks down over a period of months to become sometimes invisible. Perhaps the best example of this is the cavity left by the removal of the slough from a large carbuncle; in a very few months there is a small white, irregular scar marking the centre of the great cavity where the carbuncle existed. If the wound has involved other tissues than connective tissue - for instance, the mucousmembrane of the cheek, or the skin - then the very specialised epithelial lining also grows across as a sheet of cells and covers up the granulation tissue. The same process occurs in the intestinal tract; when an anastomosis (artificial opening between two hollow organs or vessels) has been performed, the cut edges of the mucousmembrane are stuck together temporarily by fibrin, and over a period of days the cells lining the stomach or intestine grow rapidly across the gap. When a bone is broken, repair takes place in a similar way: calcium substances from the blood are deposited in the granulation tissue forming callus. Into this callus the specialised cells which form true bone, migrate from the surrounding damaged bone: over a period of weeks or even months the minute structure is rebuilt to join up exactly with the bone on either side of the break.
The healing power of the body is influenced by many factors. An adequate supply of oxygen is necessary for these tissue repairs, and as oxygen is carried to the tissues by the blood, anaemia results in a very poor healing rate. Vitamins, especially vitamin C, are necessary for the repair of tissues, so that patients whose reserve of vitamin C has been depleted heal more slowly and may in fact not heal at all. Patients who are ill use more vitamin C than the normal healthy individuals and sometimes, unless their requirement is met, a wound may come apart even a week or more after operation, showing no sign of healing whatever. Infection always delays healing as it interferes with the activities of the cells at the edges of the wound. Similarly, if the patient' s general health has been impaired by longstanding disease or bad nourishment his powers of healing are poor, as the substances required for the repair are in short supply. The presence of foreign bodies or a poor blood supply (such as occurs in arteriosclerosis, or if the stitches have been tied too tight) will also delay sound healing. In addition, there are many personal and undetermined factors which must be responsible for the fact that some people heal quickly and others heal very poorly. Age is important; babies and children repair their tissues very much more rapidly than old people. This is because the growing child has much more vitality in all his cells. For example, a fracture of the humerus in a new-born baby may be soundly united in ten days; in an adult the same fracture requires about eight weeks to heal. Research Tissue Repair and Replacement
Albumen or albumin is a substance, or rather group of substances, so named from the Latin for the white of an egg (albus) , which is one of its most abundant known forms. It may be taken as the type of the protein compounds or the nitrogenous class of food stuffs. One variety enters largely into the composition of the animal fluids and solids, is coagulable by heat at and above 160 degrees, and is composed of carbon, hydrogen, nitrogen, and oxygen, with a little sulphur. It abounds in the serum of the blood, the vitreous and crystalline humours of the eye, the fluid of dropsy, the substance called coagulable lymph, in nutritive matters, the juice of flesh, etc. The blood contains about seven percent of albumen. Another variety called vegetable albumen exists in most vegetable juices and many seeds, and has nearly the same composition and properties as egg albumen. When albumen coagulates in any fluid it readily encloses any substances that may be suspended in the fluid. Hence it is used to clarify syrupy liquors. In cookery white of eggs is employed for clarifying, but in large operations like sugar-refining the serum of blood is used. From its being coagulable by various salts, and especially by corrosive sublimate, with which it forms an insoluble compound, white of egg is a convenient antidote in cases of poisoning by that substance. With lime it forms a cement to mend broken ware.
In botany the name albumen is given to the farinaceous matter which surrounds the embryo, the term in this case having no reference to chemical composition. It constitutes the meat of the cocoa-nut, the flour or meal of cereals, the roasted part of coffee, etc. Research Albumen
Borax or sodium tetraborate has long been obtained under the name of tincal, from India, the main source being not India but a series of lakes in Tibet. As imported it was in small pieces of a dirty yellowish colour, and was covered with a fatty or soapy matter. Tincal, which contains various impurities, was formerly the only source of borax; but besides Tuscany other sources of boric acid, more particularly in North and South America, and the salt mines at Stassfurt, etc, in Germany, were rendered available. North America yields large quantities, there being rich deposits of borax and boracic minerals on the Pacific slope. Pure borax forms large transparent six-sided prisms, which dissolve readily in water, effloresce in dry air, and when heated melt in their water of crystallization, swell up, and finally fuse to a transparentglass.
Borax has a variety of uses. In medicine it is employed in ulcerations and skin diseases, and its cleansing properties render it useful for various domestic purposes. It has valuable antiseptic and disinfecting properties, and is now much used for the preservation of meat, fish, and milk, especially meat. It is also employed in the soldering of metals, and in making fine glaze for porcelain, as it renders the materials more fusible. It is used as an ingredient of enamels, and in making beads, glass, and cement. It is also one of the mordants employed in calico-printing. Research Borax
Canada Balsam is a fluid oleoresin obtained from the balsam fir, common in Canada and the USA. Canada balsam solidifies upon exposure to the air, but remains plastic. It is used in medicine, microscopy and as a plasticiser in making varnish and was at one time used as a cement in the manufacture of compound lenses by opticians as its refractive index is almost as good as that of glass. Research Canada Balsam
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Cement
