ANOPLURA

the anoplura or lice (see louse) are wingless parasitic insects (fig. 14) forming an order distinct from the hemiptera, their sucking and piercing mouth-organs being apparently formed on quite a different plan from those of the heteroptera and homoptera. in front of the head is a short tube armed with strong recurved hooks which can be fixed into the skin of the host, and from the tube an elongate more slender sucking-trunk can be protruded (fig. 15). each foot is provided with a single strong claw which, opposed to a process on the shin, serves to grasp a hair of the host, all the lice being parasites on different mammals. although g. enderlein has recently shown that the jaws of the hemiptera can be recognized in a reduced condition in connexion with the louse's proboscis, the modification is so excessive that the group certainly deserves ordinal separation. bibliography.--a recent standard work on the morphology of the hemiptera by r. heymons (_nova acta acad. leop. carol._ lxxiv. 3, 1899) contains numerous references to older literature. an excellent survey of the order is given by d. sharp (_cambridge nat. hist._ vol. vi., 1898). for internal structure of heteroptera see r. dufour, _mem. savans etrangers_ (paris, iv., 1833); of homoptera, e. witlaczil (_arb. zool. inst. wien_, iv., 1882, _zeits. f. wiss. zool._ xliii., 1885). the development of aphids has been dealt with by t. h. huxley (_trans. linn. soc._ xxii., 1858) and e. witlaczil (_zeits. f. wiss. zool._ xl., 1884). fossil hemiptera are described by s. h. scudder in k. zittel's _paleontologie_ (french translation, vol. ii. paris, 1887, and english edition, vol. i., london, 1900), and by a. handlirsch (_verh. zool. bot. gesell. wien_, lii., 1902). among general systematic works on heteroptera may be mentioned j. c. schiodte (_ann. mag. nat. hist._ (4) vi., 1870); c. stal's _enumeratio hemipterorum_ (_k. svensk. vet. akad. handl._ ix.-xiv., 1870-1876); l. lethierry and g. severin's _catalogue generale des hemipteres_ (brussels 1893, &c.); g. c. champion's volumes in the _biologia centrali-americana_; w. l. distant's oriental cicadidae (london, 1889-1892), and many other papers; m. e. fernald's _catalogue of the coccidae_ (amherst, u.s.a., 1903). european hemiptera have been dealt with in numerous papers by a. puton. for british species we have e. saunders's _hemiptera-heteroptera of the british isles_ (london, 1892); j. edwards's hemiptera-homoptera of the british isles (london, 1896); j. b. buckton's _british aphidae_ (london, ray society, 1875-1882); and r. newstead's _british coccidae_ (london, ray society, 1901-1903). aquatic hemiptera are described by l. c. miall (_nat. history aquatic insects_; london, 1895), and by g. w. kirkaldy in numerous recent papers (_entomologist_, &c.). for marine hemiptera (_halobates_) see f. b. white (_challenger reports_, vii., 1883); j. j. walker (_ent. mo. mag._, 1893); n. nassonov (warsaw, 1893), and g. h. carpenter (_knowledge_, 1901, and _report, pearl oyster fisheries, royal society_, 1906). sound-producing organs of heteroptera are described by a. handlirsch (_ann. hofmus. wien_, xv. 1900), and g. w. kirkaldy (_journ. quekett club_ (2) viii. 1901); of cicads by g. carlet (_ann. sci. nat. zool._ (6) v. 1877). for the anoplura see e. piaget's _pediculines_ (leiden, 1880-1905), and g. enderlein (_zool. anz._ xxviii., 1904). (g. h. c.) hemlock (in o. eng. _hemlic_ or _hymlice_; no cognate is found in any other language, and the origin is unknown), the _conium maculatum_ of botanists, a biennial umbelliferous plant, found wild in many parts of great britain and ireland, where it occurs in waste places on hedge-banks, and by the borders of fields, and also widely spread over europe and temperate asia, and naturalized in the cultivated districts of north and south america. it is an erect branching plant, growing from 3 to 6 ft. high, and emitting a disagreeable smell, like that of mice. the stems are hollow, smooth, somewhat glaucous green, spotted with dull dark purple, as alluded to in the specific name, _maculatum_. the root-leaves have long furrowed footstalks, sheathing the stem at the base, and are large, triangular in outline, and repeatedly divided or compound, the ultimate and very numerous segments being small, ovate, and deeply incised at the edge. these leaves generally perish after the growth of the flowering stem, which takes place in the second year, while the leaves produced on the stem became gradually smaller upwards. the branches are all terminated by compound many-rayed umbels of small white flowers, the general involucres consisting of several, the partial ones of about three short lanceolate bracts, the latter being usually turned towards the outside of the umbel. the flowers are succeeded by broadly ovate fruits, the mericarps (half-fruits) having five ribs which, when mature, are waved or crenated; and when cut across the albumen is seen to be deeply furrowed on the inner face, so as to exhibit in section a reniform outline. the fruits when triturated with a solution of caustic potash evolve a most unpleasant odour. hemlock is a virulent poison, but it varies much in potency according to the conditions under which it has grown, and the season or stage of growth at which it is gathered. in the first year the leaves have little power, nor in the second are their properties developed until the flowering period, at which time, or later on when the fruits are fully grown, the plant should be gathered. the wild plant growing in exposed situations is to be preferred to garden-grown samples, and is more potent in dry warm summers than in those which are dull and moist. the poisonous property of hemlock resides chiefly in the alkaloid _conine_ or _conia_ which is found in both the fruits and the leaves, though in exceedingly small proportions in the latter. conine resembles nicotine in its deleterious action, but is much less powerful. no chemical antidote for it is known. the plant also yields a second less poisonous crystallizable base called _conhydrine_, which may be converted into conine by the abstraction of the elements of water. when collected for medicinal purposes, for which both leaves and fruits are used, the former should be gathered at the time the plant is in full blossom, while the latter are said to possess the greatest degree of energy just before they ripen. the fruits are the chief source whence conine is prepared. the principal forms in which hemlock is employed are the extract and juice of hemlock, hemlock poultice, and the tincture of hemlock fruits. large doses produce vertigo, nausea and paralysis; but in smaller quantities, administered by skilful hands, it has a sedative action on the nerves. it has also some reputation as an alterative and resolvent, and as an anodyne. the acrid narcotic properties of the plant render it of some importance that one should be able to identify it, the more so as some of the compound-leaved umbellifers, which have a general similarity of appearance to it, form wholesome food for man and animals. not only is this knowledge desirable to prevent the poisonous plant being detrimentally used in place of the wholesome one; it is equally important in the opposite case, namely, to prevent the inert being substituted for the remedial agent. the plant with which hemlock is most likely to be confounded is _anthriscus sylvestris_, or cow-parsley, the leaves of which are freely eaten by cattle and rabbits; this plant, like the hemlock, has spotted stems but they are hairy, not hairless; it has much-divided leaves of the same general form, but they are downy and aromatic, not smooth and nauseous when bruised; and the fruit of _anthriscus_ is linear-oblong and not ovate. hemp (in o. eng. _henep_, cf. dutch _hennep_, ger. _hanf_, cognate with gr. [greek: kannabis], lat. _cannabis_), an annual herb (_cannabis sativa_) having angular rough stems and alternate deeply lobed leaves. the bast fibres of _cannabis_ are the hemp of commerce, but, unfortunately, the products from many totally different plants are often included under the general name of hemp. in some cases the fibre is obtained from the stem, while in others it comes from the leaf. sunn hemp, manila hemp, sisal hemp, and phormium (new zealand flax, which is neither flax nor hemp) are treated separately. all these, however, are often classed under the above general name, and so are the following:--deccan or ambari hemp, _hibiscus cannabinus_, an indian and east indian malvaceous plant, the fibre from which is often known as brown hemp or bombay hemp; pite hemp, which is obtained from the american aloe, _agave americana_; and moorva or bowstring-hemp, _sansevieria zeylanica_, which is obtained from an aloe-like plant, and is a native of india and ceylon. then there are canada hemp, _apocynum cannabinum_, kentucky hemp, _urtica cannabina_, and others. the hemp plant, like the hop, which is of the same natural order, cannabinaceae, is dioecious, i.e. the male and female flowers are borne on separate plants. the female plant grows to a greater height than the male, and its foliage is darker and more luxuriant, but the plant takes from five to six weeks longer to ripen. when the male plants are ripe they are pulled, put up into bundles, and steeped in a similar manner to flax, but the female plants are allowed to remain until the seed is perfectly ripe. they are then pulled, and after the seed has been removed are retted in the ordinary way. the seed is also a valuable product; the finest is kept for sowing, a large quantity is sold for the food of cage birds, while the remainder is sent to the oil mills to be crushed. the extracted oil is used in the manufacture of soap, while the solid remains, known as oil-cake, are valuable as a food for cattle. the leaves of hemp have five to seven leaflets, the form of which is lanceolate-acuminate, with a serrate margin. the loose panicles of male flowers, and the short spikes of female flowers, arise from the axils of the upper leaves. the height of the plant varies greatly with season, soil and manuring; in some districts it varies from 3 to 8 ft., but in the piedmont province it is not unusual to see them from 8 to 16 ft. in height, whilst a variety (_cannabis sativa_, variety gigantea) has produced specimens over 17 ft. in height. all cultivated hemp belongs to the same species, _cannabis sativa_; the special varieties such as _cannabis indica_, _cannabis chinensis_, &c., owe their differences to climate and soil, and they lose many of their peculiarities when cultivated in temperate regions. rumphius (in the 17th century) had noticed these differences between indian and european hemp. wild hemp still grows on the banks of the lower ural, and the volga, near the caspian sea. it extends to persia, the altai range and northern and western china. the authors of the _pharmacographia_ say:--"it is found in kashmir and in the himalaya, growing 10 to 12 ft. high, and thriving vigorously at an elevation of 6000 to 10,000 ft." wild hemp is, however, of very little use as a fibre producer, although a drug is obtained from it. it would appear that the native country of the hemp plant is in some part of temperate asia, probably near the caspian sea. it spread westward throughout europe, and southward through the indian peninsula. the names given to the plant and to its products in different countries are of interest in connexion with the utilization of the fibre and resin. in sans. it is called _goni_, _sana_, _shanapu_, _banga_ and _ganjika_; in bengali, _ganga_; pers. _bang_ and _canna_; arab. _kinnub_ or _cannub_; gr. _kannabis_; lat. _cannabis_; ital. _canappa_; fr. _chanvre_; span. _canamo_; portuguese, _canamo_; russ. _konopel_; lettish and lithuanian, _kannapes_; slav. _konopi_; erse, _canaib_ and _canab_; a. sax. _hoenep_; dutch, _hennep_; ger. _hanf_; eng. _hemp_; danish and norwegian, _hamp_; icelandic, _hampr_; and in swed. _hampa_. the english word _canvas_ sufficiently reveals its derivation from _cannabis_. very little hemp is now grown in the british isles, although this variety was considered to be of very good quality, and to possess great strength. the chief continental hemp-producing countries are italy, russia and france; it is also grown in several parts of canada and the united states and india. the central provinces, bengal and bombay are the chief centres of hemp cultivation in india, where the plant is of most use for narcotics. the satisfactory growth of hemp demands a light, rich and fertile soil, but, unlike most substances, it may be reared for a few years in succession. the time of sowing, the quantity of seed per acre (about three bushels) and the method of gathering and retting are very similar to those of flax; but, as a rule, it is a hardier plant than flax, does not possess the same pliability, is much coarser and more brittle, and does not require the same amount of attention during the first few weeks of its growth. the very finest hemp, that grown in the province of piedmont, italy, is, however, very similar to flax, and in many cases the two fibres are mixed in the same material. the hemp fibre has always been valuable for the rope industry, and it was at one time very extensively used in the production of yarns for the manufacture of sail cloth, sheeting, covers, bagging, sacking, &c. much of the finer quality is still made into cloth, but almost all the coarser quality finds its way into ropes and similar material. a large quantity of hemp cloth is still made for the british navy. the cloth, when finished, is cut up into lengths, made into bags and tarred. they are then used as coal sacks. there is also a quantity made into sacks which are intended to hold very heavy material. hemp yarns are also used in certain classes of carpets, for special bags for use in cop dyeing and for similar special purposes, but for the ordinary bagging and sacking the employment of hemp yarns has been almost entirely supplanted by yarns made from the jute fibre. hemp is grown for three products--(1) the fibre of its stem; (2) the resinous secretion which is developed in hot countries upon its leaves and flowering heads; (3) its oily seeds. hemp has been employed for its fibre from ancient times. herodotus (iv. 74) mentions the wild and cultivated hemp of scythia, and describes the hempen garments made by the thracians as equal to linen in fineness. hesychius says the thracian women made sheets of hemp. moschion (about 200 b.c.) records the use of hempen ropes for rigging the ship "syracusia" built for hiero ii. the hemp plant has been cultivated in northern india from a considerable antiquity, not only as a drug but for its fibre. the anglo-saxons were well acquainted with the mode of preparing hemp. hempen cloth became common in central and southern europe in the 13th century. _hemp-resin._--hemp as a drug or intoxicant for smoking and chewing occurs in the three forms of bhang, ganja and charas. 1. _bhang_, the hindustani _siddhi_ or _sabzi_, consists of the dried leaves and small stalks of the hemp; a few fruits occur in it. it is of a dark brownish-green colour, and has a faint peculiar odour and but a slight taste. it is smoked with or without tobacco; or it is made into a sweetmeat with honey, sugar and aromatic spices; or it is powdered and infused in cold water, yielding a turbid drink, _subdschi_. _hashish_ is one of the arabic names given to the syrian and turkish preparations of the resinous hemp leaves. one of the commonest of these preparations is made by heating the bhang with water and butter, the butter becoming thus charged with the resinous and active substances of the plant. 2. _ganja_, the guaza of the london brokers, consists of the flowering and fruiting heads of the female plant. it is brownish-green, and otherwise resembles bhang, as in odour and taste. some of the more esteemed kinds of hashish are prepared from this ganja. ganja is met with in the indian bazaars in dense bundles of 24 plants or heads apiece. the hashish in such extensive use in central asia is often seen in the bazaars of large cities in the form of cakes, 1 to 3 in. thick, 5 to 10 in. broad and 10 to 15 in. long. 3. _charas_, or churrus, is the resin itself collected, as it exudes naturally from the plant, in different ways. the best sort is gathered by the hand like opium; sometimes the resinous exudation of the plant is made to stick first of all to cloths, or to the leather garments of men, or even to their skin, and is then removed by scraping, and afterwards consolidated by kneading, pressing and rolling. it contains about one-third or one-fourth its weight of the resin. but the churrus prepared by different methods and in different countries differs greatly in appearance and purity. sometimes it takes the form of egg-like masses of greyish-brown colour, having when of high quality a shining resinous fracture. often it occurs in the form of irregular friable lumps, like pieces of impure linseed oil-cake. the medicinal and intoxicating properties of hemp have probably been known in oriental countries from a very early period. an ancient chinese herbal, part of which was written about the 5th century b.c., while the remainder is of still earlier date, notices the seed and flower-bearing kinds of hemp. other early writers refer to hemp as a remedy. the medicinal and dietetic use of hemp spread through india, persia and arabia in the early middle ages. the use of hemp (bhang) in india was noticed by garcia d'orta in 1563. berlu in his _treasury of drugs_ (1690) describes it as of "an infatuating quality and pernicious use." attention was recalled to this drug, in consequence of napoleon's egyptian expedition, by de sacy (1809) and rouger (1810). its modern medicinal use is chiefly due to trials by dr o'shaughnessy in calcutta (1838-1842). the plant is grown partly and often mainly for the sake of its resin in persia, northern india and arabia, in many parts of africa and in brazil. _pharmacology and therapeutics._--the composition of this drug is still extremely obscure; partly, perhaps, because it varies so much in individual specimens. it appears to contain at least two alkaloids--cannabinine and tetano-cannabine--of which the former is volatile. the chief active principle may possibly be neither of these, but the substance cannabinon. there are also resins, a volatile oil and several other constituents. cannabis indica--as the drug is termed in the pharmacopoeias--may be given as an extract (dose (1/4)-1 gr.) or tincture (dose 5-15 minims). the drug has no external action. the effects of its absorption, whether it be swallowed or smoked, vary within wide limits in different individuals and races. so great is this variation as to be inexplicable except on the view that the nature and proportions of the active principles vary greatly in different specimens. but typically the drug is an intoxicant, resembling alcohol in many features of its action, but differing in others. the early symptoms are highly pleasurable, and it is for these, as in the case of other stimulants, that the drug is so largely consumed in the east. there is a subjective sensation of mental brilliance, but, as in other cases, this is not borne out by the objective results. it has been suggested that the incoordination of nervous action under the influence of indian hemp may be due to independent and non-concerted action on the part of the two halves of the cerebrum. following on a decided lowering of the pain and touch senses, which may even lead to complete loss of cutaneous sensation, there comes a sleep which is often accompanied by pleasant dreams. there appears to be no evidence in the case of either the lower animals or the human subject that the drug is an aphrodisiac. excessive indulgence in cannabis indica is very rare, but may lead to general ill-health and occasionally to insanity. the apparent impossibility of obtaining pure and trustworthy samples of the drug has led to its entire abandonment in therapeutics. when a good sample is obtained it is a safe and efficient hypnotic, at any rate in the case of a european. the tincture should not be prescribed unless precautions are taken to avoid the precipitation of the resin which follows its dilution with water. see watt, _dictionary of the economic products of india_.