Horn is a general term applied to all hard and pointed appendages of the head, as in deer, cattle, etc, but as a term denoting a particular kind of substance nothing should be called horn which is not derived from the epidermis or outer, layer of the integument, whether on the trunk, hoofs, or head.
Horn is a tough, flexible, semi-transparent substance, most liberally developed in the horns of bovine animals, but also found in connection with the 'shell' of the tortoise, the nails, claws, and hoofs of animals, the beak of bird and turtle, etc
Horn is softened very completely by heat, so as to become readily flexible, and to adhere to other pieces similarly softened. True horn consists principally of an albuminoid principle, keratin, with a small portion of gelatine and a little phosphate of lime. In some species of animals the males only have horns, as for instance the stag. In cattle both male and female have horns, though there are also hornless cattle.
Horns differ widely in the case of different animals. Thus the horns of deer consist of bone, and are deciduous; those of the giraffe are independent bones, with a covering of hairy skin; those of oxen, sheep, and antelopes consist of a bony core covered by a horny sheath. The horns of the rhinoceros alone consist exclusively of horny matter. The horns of oxen, sheep, goats, and antelopes are never shed, except in the case of the prong-horned antelope. The number never normally exceeds four, and in the case of deer the horns are branched.
The various kinds of horns were formerly employed for many purposes. The principal formerly used in the arts are those of the ox, buffalo, sheep, and goat. Deer horns were almost exclusively employed for the handles of knives and of sticks and umbrellas. Those which furnish true horn can be softened by heat (usually in boiling water), cut into sheets of various thickness, which sheets may be soldered or welded together at the edges so as to form plates of large dimensions, and were formerly polished and dyed so as to imitate the much more expensive tortoise-shell. The clippings of horn may be welded together in the same manner, and were formerly made into snuff-boxes, powder horns, handles for umbrellas, knives, forks, etc. As horn has the valuable property of taking on and retaining a sharp impression from a die, many highly ornamental articles were also turned out. Combs for the hair were made from the flattened sheets, and out of the solid parts of buffalo horns beautiful carvings were made. Research Horn
In its narrow, everyday use, vegetable is a word indicating any herb that is cultivated specially for table use in whole or part, such as the turnip (root), cabbage (leaves), broccoli (flowers), peas and beans (fruit). In its widest sense it includes all living things that are not animals - trees, shrubs, herbs, ferns, mosses, seaweeds, fungi, and the microscopic diatoms.
The unit of structure, the cell, is essentially the same in both animals and plants, but the combination of the cells into tissues and organs shows marked differences.
All animals depend for their food upon material originally elaborated by plants. The green plants alone have the power to construct this basic food material from elemental substances, and physiological processes different from those of animal assimilation are rendered necessary. The fungi approach the animals in this respect: they must feed upon material that has already done service as part of the structure of other plants or of animals.
The fine divisions of roots explore the soil in search of water in which are dissolved the salts of sodium, iron, potassium, phosphorus, calcium, sulphur, etc. The hairs with which the rootlets are clothed absorb this fluid by osmosis, and it is passed upward through the long vessels of the wood bundles until it reaches the cells of the leaf. These cells contain green bodies (chloroplasts) in their protoplasm, and it is these that impart the green colour to leaves and soft shoots. In the leaf-skin (epidermis) there are innumerable pores or stomata through which surplus water from the roots is evaporated and through which atmospheric air is admitted to the spaces between the leaf-cells.
The chloroplasts in these cells have the power to utilise solar energy in decomposing the carbon dioxide of the air, and the cells retain the carbon, setting free the oxygen. Water from the roots is broken up also into its elements, hydrogen and oxygen, and with these plus carbonstarch is formed. This, converted into grape sugar, is passed from cell to cell to parts of the plant whore it is needed for the production of new cells, wood, bark, leaves, or fruit. Starch is the material from which are made all the organic substances produced by the plant.
The surplus over present requirements is stored up as reserves in seeds, enlarged roots or stems, bulbs, or tubers for renewed growth or floral display at a later season. Waste products are converted into resins, oils/wax, or alkaloids - many of these being of considerable economic value to man. Part of the water stream from the roots passes by osmosis from cell to cell, where it is necessary in order to keep the protoplasm in an active condition; any insufficiency is followed by a flagging of the tissues, the drooping of leaves and young shoots. In addition to the absorption of carbon by the protoplasts for building purposes, the leaf-cells also take up oxygen from the atmosphere and give off carbon much as animals do.
As the plant respires without lungs and assimilates without digestive organs, so also it can effect movements without a muscular system and react to external stimuli without a nervous system. It is sensitive to light and heat; many plants have distinct night and day positions for their leaves. It responds positively and negatively to the force of gravity, the root going down into the earth and the stem rising into the air. The growing tip of a stem or shoot commonly nutates, i.e. moves from side to side or in a circle or ellipse. The plant can orientate itself, i.e. take up a definite position in regard to the incidence of light or other external stimulus. These movements appear to be controlled largely by alterations in the position of the mobile chloroplasts.
The reproductive process is, in essentials, similar to that of animals, the ovules or seed-eggs in the ovary requiring to be fertilised by male sperms represented by the pollen grains produced in the anthers. The result of such fertilisation is to cause the ovule to develop into an embryo capable of further development under suitable conditions into a plant resembling the parent. Research Vegetable
Dermatophyte is a parasitic plant, chiefly of the lowest type of the Cryptogamia, infesting the cuticle and epidermis of people and animals, and giving rise to various forms of skin-disease, such as ringworm, etc. Research Dermatophyte
The Ferns (Filices) are a natural order of cryptogamous or flowerless plants, forming the highest group of the acrogena or summit-growers. They are leafy plants, the leaves, or more properly fronds, arising from a rhizome or root-stock, or from a hollow arborescent trunk, and being circinate in vernation, a term descriptive of the manner in which the fronds are rolled up before they are developed in spring, having then the appearance of a bishop's crosier. On the veins of their lower surface, or their margins, the fronds bear small vessels named sporangia, containing spores. These spore-cases are arrangod in clusters, named sori, which are either naked or covered with a layer of the epidermis, which forms an involucre or indusium. When the spores germinate they produce a cellular structure of a leafy description, called the pro-embryo, or prothallus, upon which are developed organs which have received the names of antheridia and archegonia. When produced upon the prothallus these organs do not immediately give origin to a germinating spore, but from their mutual action proceeds a distinct cellular body, destined at a later period to develop into a fruit-bearing frond.
Ferns have a wide geographical range, but are most abundant in humid, temperate, and tropical regions. In the tropical forests the tree-ferns rival the palms, rising sometimes to a height of 15 or 18 metres. Ferns are very abundant as fossil plants. The earliest-known forms occur in Devonian rocks. Various systems of classification for ferns have been proposed over time. The order is usually divided into six or eight suborders or tribes distinguished by differences in the structure of the sporangium. The generic characters are founded on the position and direction of the sori and on the venation. The largest division is that of the Polypodiaceae, to which nearly all British ferns belong, such as the polypody, the lady-fern, the bracken, the hard-fern, the spleenwort, the maiden-hair, the hart's-tonguefern, etc. The royal fern, however, belongs to the Osmundaceae. A few of the ferns are used medicinally, mostly as demulcents and astringents. Some yield food. Pteris esculenta is the edible bracken of New Zealand. Research Ferns
The Phylum annelida are the segmented worms. They are triploblastic, metamerically segmented, coelomate metazoa. The body wall is covered by a glandular epidermis and comprised of longitudinal and circular muscles. Research Phylum Annelida
Phylum nematoda are the roundworms. They are triploblastic animals with elongated, spindle-shaped bodies. A respiratory and blood vascular system are both lacking. The epidermis secretes a tough cuticle. Cilia are lacking. The roundworms are to be found everywhere that life can be supported. Research Phylum nematoda
Pipa is a genus of aquatic tongueless toad of the order Aglossa. The head is depressed and triangular in shape; the skin is covered with small tubercles; the digits on the fore limb are slender, and free from one another, and furnished with star-shaped processes at the tip, while those on the hind limbs are broadly webbed. The genus is peculiar for the habit which the female possesses of carrying the eggs until they hatch in little pockets in the skin of her back. As the eggs are laid they are spread out over the back, the male assisting the process; each egg then sinks into a pouch of the epidermis, which is subsequently closed by a lid. From these skin pockets emerge the young after about three months, and then resemble the parents except in size, the gilled tadpole stage being omitted from the life history. Research Pipa
Adipose tissue is one of the many different types of connective tissue found in the human body. Connective tissue composes the dermis of the skin. Unlike the cells of the epithelial layer of the epidermis, which are crowded close together, the cells of connective tissue are scattered far apart with many fibres between them. Adipose tissue is a metabolically active tissue that stores fat and releases it in response to a variety of nervous and hormonal stimuli. It also acts as an insulator to help maintain body temperature and acts as a protective padding in certain areas. Adipose tissue is also found in bonemarrow. Research Adipose tissue
The dermal papillae are small, nipple-like protrusions of the dermis that reach into the epidermis, bringing food and oxygen to the lower layers of epidermal cells. In addition, a papilla nourishes every hair follicle. Rows of papillae protruding from the dermis into the epidermis form ridges that create patterns on the skin of the hands, feet, and body. These papillary ridges on the fingertips are responsible for fingerprints. These ridges develop sometime before birth. Not only is the pattern unique for each individual, but also it never changes except to grow larger. Research Dermal Papillae
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Horn
