Head is the term applied to the anterior part of the body of an animal when marked off by a difference in size, or by a constriction (neck). A gradual increase of complexity in the structure of the head is observable as we ascend from the lowest to the highest forms of life. In the Protozoa, Infusoria, and Coelenterates nothing that can be regarded as a head is found, and it is not until we ascend to the worms proper, the articulated animals (crustaceans, myriapods, spiders, and insects), the land and fresh-water gasteropods (snails and whelks), and the cuttle-fishes, that a head proper is found.
The cuttle-fishes have a remarkable cartilaginous box, which, like a skull, protects their anterior nervous ganglia and gives support to the muscles. The head of the vertebrated animals presents a regular series of increasing complexity from the lancelet upwards, and as the anterior nervous mass enlarges, and its ganglia increase in complexity, so do the anterior vertebra change their character; as the brain becomes specialized, so does the brain-case or skull, attaining its highest development in man.
In man, and in the higher vertebrates, the head consists of an upper chamber, lodging the brain, the eyes, and other sense organs, and a lower, lodging the first portion of the alimentarycanal. In proportion as the vertebrates become developed, the brain increases in size, and its position advances anteriorly, until, in man, it comes to overhang the face.
Head is the unit of measurement of cattle. Thus a herd of 100 cattle is referred to as 100 head.
Acamthocephala are a compact group of cylindrical, parasitic worms, with no near allies in the animal kingdom. Its members are quite devoid of any mouth or alimentarycanal, but have a well-developed body cavity into which the eggs are dehisced and which communicates with the exterior by means of an oviduct. The size of the animals varies greatly, from some forms a few millimetres in length to Gigantorhynchus gigas, which measures from ten to 65 centimetres. The adults live in great numbers in the alimentarycanal of some vertebrate, usually fish, the larvae are as a rule encysted in the body cavity of some invertebrate, most often an insect or crustacean, more rarely a small fish. The body is divisible into a proboscis and a trunk with sometimes an intervening neck region. Research Acamthocephala
The alimentary canal is a tube beginning at the mouth and passing through the body to the anus. It is primarily used for the reception of food. Research Alimentary canal
Carnivora is a term applicable to any creatures that feed on flesh or animal substances, but is now applied specially to an order of mammals which prey upon other animals. The head is small, the jaws powerful, and the skin is well covered with hair. Two sets of teeth, deciduous or milk and permanent, are always developed in succession, and in both sets incisors, canines, and molars are distinguishable. The stomach is simple and the alimentarycanal short, thus making the body as light and slender as possible for the purpose of hunting and springing on its prey.
The muscular activity of the Carnivora is very great, their respiration and circulation very active, and their demand for food is consequently constant. Carnivora are often divided into Plantigrada, comprising the bears, badgers, raccoons, etc; Digitigrada, comprising lions, tigers, cats, dogs; and Pinnipedia or Pinnigrada, comprising the seals and walruses. The two former divisions are also classed together as Fissipedia. The typical Plantigrada are distinguished by their putting the whole sole of the foot to the ground in walking, while the Digitigrada walk on the tips of their toes. The Plantigrada are also less decidedly carnivorous, and feed much on roots, honey, and fruits. In the Pinnigrada the body is long and of a fish shape, the fore and hind limbs are short and form broad webbed swimming-paddles. The hind-feet are placed far back, and more or less tied down. to the tail by the integuments. Research Carnivora
Cestoda (the Cestodes) is a class of Phylum platyhelminthes commonly known as the tapeworms. They are internal parasites lacking an alimentarycanal. They have no definite sense organs, and the nervous system is poorly developed. The cuticle is thick and many-layered. Hooks and/or suckers are limited to one end. They have great reproductive powers, both sexual and asexual. Research Cestoda
Coelentera (Coelenterata) are a sub-kingdom of animals, including those whose alimentarycanal communicates freely with the general cavity of the body ('the somatic cavity'). The body is essentially composed of two layers or membranes, an outer layer or 'ectoderm' and an inner layer or 'endoderm.' No circulatory organs exist, and in most there are no traces of a nervous system. Peculiar stinging organs or 'thread-cells' are usually, if not always, present, and in most cases there is a radiate or starlike arrangement of the organs, which is especially perceptible in the tentacles, which are in most instances placed round the mouth. Distinct reproductive organs exist in all, but multiplication also takes place by fission and budding. The Coelentera are divided into two great sections, the Actinozoa and the Hydrozoa, and include the medusas, corals, sea-anemones, etc. They are nearly all marine animals. Research Coelentera
Entomology is the branch of zoology dealing with insects. It was started as a science in 1705 by the publication of Ray's 'Methodus Insectorum'.
The name entomology comes from the Greek entoma, animals 'cut in', the transverse division or segmentation of the body being their most conspicuous feature.
The true insects are those animals of the division Arthropoda or Articulata distinguished from the other classes of the division by the fact that the three divisions
of the body - the head, thorax, and abdomen - are always distinct from one another. There are never more than three pairs of legs in the perfect insect, and these are all borne upon the thorax. Each leg consists of from six to nine joints. The first of these is called the 'coxa,' and is succeeded by a short joint called the 'trochanter.' This is followed by a joint, often of large size, called the 'femur,' succeeded by the 'tibia,' and this has articulated to it the 'tarsus', which may be composed of from one to five joints.
Normally two pairs of wings are present, but one or other may be wanting. The wings are expansions of the sides of the second and third sections of the thorax, and are attached by slender tubes called 'nervures'.
In the beetles the anterior pair of wings becomes hardened so as to form protective cases for the posterior membranous wings, and are called in this condition ' elytra ' or ' wing-cases.' Respiration is effected by means of air-tubes or tracheas, which commence at the surface of the body by lateral apertures called 'stigmata' or 'spiracles,' and ramify through every part of the body.
The head is composed of several segments amalgamated together, and carries a pair of feelers or 'antennae', a pair of eyes, usually compound, and the appendages of the mouth. The thorax is composed of three segments, also amalgamated, but generally pretty easily recognized. The abdominal segments are usually more or less freely movable upon one another, and never carry locomotive limbs; but the extremity is frequently furnished with appendages connected with generation, and which in some cases serve as offensive and defensive weapons (stings).
The organs of the mouth take collectively two typical forms, the masticatory and the suctorial, the former exemplified by the beetles, the latter by the butterflies, in which the mouth is purely for suction. The alimentarycanal consists of the oesophagus or gullet, a crop, a gizzard, a stomach, and an intestine, terminating in a cloaca. There is no regular system of blood vessels ; the most important organ of the circulation is a contractile vessel situated dorsally and called the 'dorsal vessel.' The nervous system is mainly composed of a series of ganglia placed along the ventral aspect of the body and connected by a set of double nerve-cords.
The sexes are in different individuals, and most insects are oviparous. Reproduction is generally sexual, but non-sexual reproduction also occurs. Generally the young are very different from the full-grown insect, and pass through a 'metamorphosis' before attaining the mature stage. When this metamorphosis is complete it exhibits three stages - that of the larva, caterpillar, or grub, that of the pupa or chrysalis, and that of the imago or perfect winged insect.
Insects have been divided into three sections - Ametabola,Hfemimetabola, and Holometabola, according as they undergo no metamorphosis, an incomplete one, or a complete one. The young of the Ametabola differ from the adult only in size. They are all destitute of wings; the eyes are simple and sometimes wanting. The Hemimetabola undergo an incomplete metamorphosis, the larva differing from the imago chiefly in the absence of wings and in size. The pupa is usually active, or if quiescent capable of movement. In the Holometabola the metamorphosis is complete, the larva, pupa, and imago differing greatly from one another in external appearance and habits. The larva is wormlike and the pupa quiescent. The section Ametabola (which in the opinion of many naturalists are scarcely within the pale of the true Insecta) is divided into three orders - Anoplura (lice), Mallophaga (bird-lice), and Thysanura (springtails). The section Hemimetabola comprises the orders Hemiptera (cicadas, bugs, plant-lice, etc), Orthoptera (cockroaches, crickets, grasshoppers, locusts, earwigs, etc), and Neuroptera (dragon-flies, may-flies, white-ants, etc). The Holometabola comprises the orders Aphaniptera (fleas), Diptera (gnats, bot-flies, gad-flies, mosquitos, house-flies, etc), Lepidoptera (butterflies and moths), Hymenoptera (bees, wasps, and ants), Strepsiptera (stylops, minute and parasites), and Coleoptera (ladybirds, glow-worms, cockchafers, weevils, and all of the beetle tribe).
A division is sometimes made into Mandibulate and Haustellate groups, the oral apparatus of the former being adapted for mastication, the latter for imbibition of liquid food. Both types are, however, sometimes modified, and occasionally combined. Research Entomology
Ginger is various species of perennial plant of the genus Zingiber, family Zingiberaceae found native in south east Asia, and also grown in the West Indies, South America and Africa of which Jamaican ginger is the most prized variety. Ginger grows in moist places in various parts of tropical Asia and the Asiatic islands, and was introduced into the West Indies, particularly Jamaica, as also into South America and West Africa. The rhizome, or underground stem, is what is used, being employed in various ways. It has an aromatic, pungent taste, and when young is candied, and makes an excellent preserve. It is a favourite condiment, and is used medicinally as a carminative, and in debility of the stomach and alimentarycanal. It is often useful in cases of toothache, relaxation of the uvula, and paralytic affections of the tongue. It enters into the composition of a great number of confections, infusions, pills, etc. The special preparations are the tincture and the essence of ginger; syrup, prepared by mixing twenty-five parts of syrup with one of the strong tincture. Infusion of ginger is a preparation useful for flatulence. Research Ginger
Holothuria is the typical type of an order of Echinoderms, the Holothurioidea or sea-cucumbers. This order is destitute of the calcareous plates typical of the class, but has a leathery integument open at both ends, and pierced by orifices through which suctorial feet or ambulacra protrude. They have the mouth surrounded by tentacula; a long convoluted alimentarycanal; respiratory organs near the anus, and generally in the form of two branching arborescent tubes (forming the respiratory tree) into which the water is admitted; and the organs of both sexes in each individual. They are capable of extending themselves to several times the length they have in a state of repose, and of extraordinary reproduction of parts, even of vital organs. The young undergo a metamorphosis during development. They abound in the Asiatic seas, the beche-de-mer or trepang being a member of the family. Research Holothuria
Abbreviations
Research Acamthocephala
