II. Chalarothoraca. Body protected by an investment of spicules or
fibre scattered or approximated, never fused into a continuous
skeleton.
S 1. Spicules netted or free in the protoplasm. Heterophrys Arch.
(fig. 1 (3)), Raphidiophrys Arch. (fig. 1 (4)), Pinacodocystis,
Hertw. and Less.
S 2. Spicules approximated radially. Pinaciophora Greeff,
Pompholyxophrys Arch., Lithocolla F. E. Schultze, Elaeorhanis Greeff
(in the two foregoing genera the spicules represented by sand
granules), Acanthocystis Carter (fig. 1 (5)), Pinacocystis (?)
Hertw. and Less, Myriophrys Penard. (Astrodisculus).
III. Desmothoraca. S 1 attached by a stalk. Clathrulina Cienk. (fig. 1
(2, 7)), Hedriocystis, Hertw. and Less.
S 2. Free Elaster, Grimin, Choanocystis.
_Literature._--The most important English original papers on this
group are those by W. Archer, "On some Freshwater Rhizopoda, new, or
little known," _Quarterly Journal of Microscopic Science_, N.S.
ix.-xi. (1869-1871), and "Resume of Recent Contributions to the
Knowledge of Freshwater Rhizopods," _ibid._ xvi., xvii. (1876-1877).
See also R. Hertwig and Lesser, "Uber Rhizopoda und denselben
nahestehenden Organismen," in _Archiv fur mikroscopische Anatomie_, x.
(1874), p. 35; R. Schaudinn, "Heliozoa" in _Tierreich_ (1896); E.
Penard, _Les Heliozoaires d'eau douce_ (1904); the two last named
contain full bibliographies. (M. Ha.)
HELIUM (from Gr. [Greek: helios], the sun), a gaseous chemical element,
the modern discovery of which followed closely on that of argon (q.v.).
The Investigations of Lord Rayleigh and Sir William Ramsay had shown
that indifference to chemical reagents did not sufficiently characterize
an unknown gas as nitrogen, and it became necessary to reinvestigate
other cases of the occurrence of "nitrogen" in nature. H. Miers drew
Ramsay's attention to the work of W. F. Hillebrand, who had noticed, in
examining the mineral uraninite, that an inert gas was evolved when the
mineral was decomposed with acid. Ramsay, repeating these experiments,
found that the inert gas emitted refused to oxidize when sparked with
oxygen, and on examining it spectroscopically he saw that the spectrum
was not that of argon, but was characterized by a bright yellow line
near to, but not identical with, the D line of sodium. This was
afterwards identified with the D3 line of the solar chromosphere,
observed in 1868 by Sir J. Norman Lockyer, and ascribed by him to a
hypothetical element _helium_. This name was adopted for the new gas.
Helium is relatively abundant in many minerals, all of which are
radioactive, and contain uranium or thorium as important constituents.
(For the significance of this fact see RADIOACTIVITY.) The richest known
source is thorianite, which consists mainly of thorium oxide, and
contains 9.5 cc. of helium per gram. Monazite, a phosphate of thorium
and other rare earths, contains on the average about 1 cc. per gram.
Cleveite, samarskite and fergusonite contain a little more than
monazite. The gas also occurs in minute quantities in the common
minerals of the earth's crust. In this case too it is associated with
radioactive matter, which is almost ubiquitous. In two cases, however,
it has been found in the absence of appreciable quantities of uranium
and thorium compounds, namely in beryl, and in sylvine (potassium
chloride). Helium is contained almost universally in the gases which
bubble up with the water of thermal springs. The proportion varies
greatly. In the hot springs of Bath it amounts to about one-thousandth
part of the gas evolved. Much larger percentages have been recorded in
some French springs (_Compt. rend._, 1906, 143, p. 795, and 146, p.
435), and considerable quantities occur in some natural gas (_Journ.
Amer. Chem. Soc._ 29, p. 1524). R. J. Strutt has suggested that helium
in hot springs may be derived from the disintegration of common rocks at
great depths.
Helium is present in the atmosphere, of which it constitutes four parts
in a million. It is conspicuous by its absorption spectrum in many of
the white stars. Certain stars and nebulae show a bright line helium
spectrum.
Much the best practical source of helium is thorianite, a mineral
imported from Ceylon for the manufacture of thoria. It dissolves readily
in strong nitric acid, and the helium contained is thus liberated. The
gas contains a certain amount of hydrogen and oxides of carbon, also
traces of nitrogen. In order to get rid of hydrogen, some oxygen is
added to the helium, and the mixture exploded by an electric spark. All
remaining impurities, including the excess of oxygen, can then be taken
out of the gas by Sir James Dewar's ingenious method of absorption with
charcoal cooled in liquid air. Helium alone refuses to be absorbed, and
it can be pumped off from the charcoal in a state of absolute purity. In
the absence of liquid air the helium must be purified by the methods
employed for argon (q.v.). If thorianite cannot be obtained, monazite,
which is more abundant, may be utilized. A part of the helium contained
in minerals can be extracted by heat or by grinding (J. A. Gray, _Proc.
Roy. Soc._, 1909, 82A, p. 301).
_Properties._--All attempts to make helium enter into stable chemical
union have hitherto proved unsuccessful. The gas is in all probability
only mechanically retained in the minerals in which it is found.
Jacquerod and Perrot have found that quartz-glass is freely permeable to
helium below a red-heat (_Compt. rend._, 1904, 139, p. 789). The effect
is even perceptible at a temperature as low as 220 deg. C. Hydrogen,
and, in a much less degree, oxygen and nitrogen, will also permeate
silica, but only at higher temperatures. They have made this observation
the basis of a practical method of separating helium from the other
inert gases. M. Travers has suggested that it may explain the liberation
of helium from minerals by heat, the gas being enabled to permeate the
siliceous materials in which it is enclosed. Thorianite, however,
contains no silica, and until it is shown that metallic oxides behave in
the same way this explanation must be accepted with reserve.
The density of helium has been determined by Ramsay and Travers as 1.98.
Its ratio of specific heats has very nearly the ideal value 1.666,
appropriate to a monatomic molecule. The accepted atomic weight is
accordingly double the density, i.e. approximately four times that of
hydrogen. The refractivity of helium is 0.1238 (air = 1). The solubility
in water is the lowest known, being, at 18.2 deg., only .0073 vols. per
unit volume of water. The viscosity is .96 (air = 1).
The spectrum of helium as observed in a discharge tube is distinguished
by a moderate number of brilliant lines, distributed over the whole
visual spectrum. The following are the approximate wave-lengths of the
most brilliant lines:
Red 7066
Red 6678
Yellow 5876
Green 4922
Blue 4472
Violet 4026
When the discharge passes through helium at a pressure of several
millimetres, the yellow line 5876 is prominent. At lower pressures the
green line 4922 becomes more conspicuous. At atmospheric pressure the
discharge is able to pass through a far greater distance in helium than
in the common gases.
M. Travers, G. Senter and A. Jacquerod (_Phil. Trans._ A. 1903, 200, p.
105) carefully examined the behaviour of a constant volume gas
thermometer filled with helium. For the pressure coefficient per degree,
between 0 deg. and 100 deg. C., they give the value .00366255, when the
initial pressure is 700 mm. This value is indistinguishable from that
which they find for hydrogen. Thus at high temperatures a helium
thermometer is of no special advantage. At low temperatures, on the
other hand, they find, using an initial pressure of 1000 mm., that the
temperatures on the helium scale are measurably higher than on the
hydrogen scale, owing to the more perfectly gaseous condition of helium.
This difference amounts to about 1/10 deg. at the temperature of liquid
oxygen, and about 1/5 deg. at that of liquid hydrogen.
The liquefaction of helium was achieved by H. Kamerlingh Onnes at Leiden
in 1908. According to him its boiling point is 4.3 deg. abs. (-268.7
deg. C.), the density of the liquid 0.154, the critical temperature 5
deg. abs., and the critical pressure 2.3 atmospheres (_Communications
from the Physical Laboratory at Leiden_, No. 108; see also LIQUID
GASES).
REFERENCES.--A bibliography and summary of the earlier work on helium
will be found in a paper by Ramsay, _Ann. chim. phys._ (1898) [7], 13,
p. 433. See also M. Travers, _The Study of Gases_ (1901).
(R. J. S.)
HELIX (Gr. [Greek: helix], a spiral or twist), an architectural term for
the spiral tendril which is carried up to support the angles of the
abacus of the Corinthian capital; from the same stalk springs a second
helix rising to the centre of the capital, its junction with one on the
opposite side being sometimes marked by a flower. Sometimes the term
"volute" is given to the angle helix, which is incorrect, as it is of a
different design and rises from the same stalk as the central helices.
Its origin is probably metallic, that is to say, it was copied from the
conventional treatment in Corinthian bronze of the tendrils of a plant.
HELL (O. Eng. _hel_, a Teutonic word from a root meaning "to cover," cf.
Ger. _Holle_, Dutch _hel_), the word used in English both of the place
of departed spirits and of the place of torment of the wicked after
death. It is used in the Old Testament to translate the Hebrew _Sheol_,
and in the New Testament the Greek [Greek: hades], Hades, and [Greek:
geenna], Hebrew _Gehenna_ (see ESCHATOLOGY).
HELLANICUS of Lesbos, Greek logographer, flourished during the latter
half of the 5th century B.C. According to Suidas, he lived for some time
at the court of one of the kings of Macedon, and died at Perperene, a
town on the gulf of Adramyttium opposite Lesbos. Some thirty works are
attributed to him--chronological, historical and episodical. Mention may
be made of: _The Priestesses of Hera at Argos_, a chronological
compilation, arranged according to the order of succession of these
functionaries; the _Carneonikae_, a list of the victors in the Carnean
games (the chief Spartan musical festival), including notices of
literary events; an _Atthis_, giving the history of Attica from 683 to
the end of the Peloponnesian War (404), which is referred to by
Thucydides (i. 97), who says that he treated the events of the years
480-431 briefly and superficially, and with little regard to
chronological sequence: _Phoronis_, chiefly genealogical, with short
notices of events from the times of Phoroneus the Argive "first man" to
the return of the Heraclidae; _Troica_ and _Persica_, histories of Troy
and Persia.
Hellanicus marks a real step in the development of historiography. He
transcended the narrow local limits of the older logographers, and was
not content to repeat the traditions that had gained general acceptation
through the poets. He tried to give the traditions as they were locally
current, and availed himself of the few national or priestly registers
that presented something like contemporary registration. He endeavoured
to lay the foundations of a scientific chronology, based primarily on
the list of the Argive priestesses of Hera, and secondarily on
genealogies, lists of magistrates (e.g. the archons at Athens), and
Oriental dates, in place of the old reckoning by generations. But his
materials were insufficient and he often had recourse to the older
methods. On account of his deviations from common tradition, Hellanicus
is often called an untrustworthy writer by the ancients themselves, and
it is a curious fact that he appears to have made no systematic use of
the many inscriptions which were ready to hand. Dionysius of
Halicarnassus censures him for arranging his history, not according to
the natural connexion of events, but according to the locality or the
nation he was describing; and undoubtedly he never, like his
contemporary Herodotus, rose to the conception of a single current of
events wider than the local distinction of race. His style, like that of
the older logographers, was dry and bald.
Fragments in Muller, _Fragmenta historicorum Graecorum_, i. and iv.;
see among older works L. Preller, _De Hellanico Lesbio historico_
(1840); Mure, _History of Greek Literature_, iv.; late criticism in H.
Kullmer, "Hellanikos" in _Jahrbucher fur klass. Philologie_
(Supplementband, xxvii. 455 sqq.) (1902), which contains new edition
and arrangement of fragments; C. F. Lehmann-Haupt, "Hellanikos,
Herodot, Thukydides," in _Klio_ vi. 127 sqq. (1906); J. B. Bury,
_Ancient Greek Historians_ (1909), pp. 27 sqq.
HELLEBORE (Gr. [Greek: helleboros]: mod. Gr. also [Greek: skaphe]: Ger.
_Nieswurz_, _Christwurz_; Fr. _hellebore_, and in the district of
Avranche, _herbe enragee_), a genus (_Helleborus_) of plants of the
natural order Ranunculaceae, natives of Europe and western Asia. They
are coarse perennial herbs with palmately or pedately lobed leaves. The
flowers have five persistent petaloid sepals, within the circle of which
are placed the minute honey-containing tubular petals of the form of a
horn with an irregular opening. The stamens are very numerous, and are
spirally arranged; and the carpels are variable in number, sessile or
stipitate and slightly united at the base and dehisce by ventral suture.
_Helleborus niger_, black hellebore, or, as from blooming in mid-winter
it is termed the Christmas rose (Ger. _Schwarze Nieswurz_; Fr., _rose de
Noel_ or _rose d'hiver_), is found in southern and central Europe, and
with other species was cultivated in the time of Gerard (see _Herball_,
p. 977, ed. Johnson, 1633) in English gardens. Its knotty root-stock is
blackish-brown externally, and, as with other species, gives origin to
numerous straight roots. The leaves spring from the top of the
root-stock, and are smooth, distinctly pedate, dark-green above, and
lighter below, with 7 to 9 segments and long petioles. The scapes, which
end the branches of the rhizome, have a loose entire bract at the base,
and terminate in a single flower, with two bracts, from the axis of one
of which a second flower may be developed. The flowers have 5 white or
pale-rose, eventually greenish sepals, 15 to 18 lines in breadth; 8 to
13 tubular green petals containing honey; and 5 to 10 free carpels.
There are several forms, the best being _maximus_. The Christmas rose is
extensively grown in many market gardens to provide white flowers forced
in gentle heat about Christmas time for decorations, emblems, &c.
_H. orientalis_, the Lenten rose, has given rise to several fine hybrids
with _H. niger_, some of the best forms being clear in colour and
distinctly spotted. _H. foetidus_, stinking hellebore, is a native of
England, where like _H. viridis_, it is confined chiefly to limestone
districts; it is common in France and the south of Europe. Its leaves
have 7- to 11-toothed divisions, and the flowers are in panicles,
numerous, cup-shaped and drooping, with many bracts, and green sepals
tinged with purple, alternating with the five petals.
_H. viridis_, or green hellebore proper, is probably indigenous in some
of the southern and eastern counties of England, and occurs also in
central and southern Europe. It has bright yellowish-green flowers, 2 to
4 on a stem, with large leaf-like bracts. O. Brunfels and H. Bock (16th
century) regarded the plant as the black hellebore of the Greeks.
_H. lividus_, holly-leaved hellebore, found in the Balearic Islands, and
in Corsica and Sardinia, is remarkable for the handsomeness of its
foliage. White hellebore is _Veratrum album_ (see VERATRUM), a
liliaceous plant.
[Illustration: _Helleborus niger_. 1, Vertical section of flower; 2,
Nectary, side and front view.]
Hellebores may be grown in any ordinary light garden mould, but thrive
best in a soil of about equal parts of turfy loam and well-rotted
manure, with half a part each of fibrous peat and coarse sand, and in
moist but thoroughly-drained situations, more especially where, as at
the margins of shrubberies, the plants can receive partial shade in
summer. For propagation cuttings of the rhizome may be taken in August,
and placed in pans of light soil, with a bottom heat of 60 deg. to 70
deg. Fahr.; hellebores can also be grown from seed, which must be sown
as soon as ripe, since it quickly loses its vitality. The seedlings
usually blossom in their third year. The exclusion of frost favours the
production of flowers; but the plants, if forced, must be gradually
inured to a warm atmosphere, and a free supply of air must be afforded,
without which they are apt to become much affected by greenfly. For
potting, _H. niger_ and its varieties, and _H. orientalis_, _atrorubens_
and _olympicus_ have been found well suited. After lifting, preferably
in September, the plants should receive plenty of light, with abundance
of water, and once a week liquid manure, not over-strong. The flowers
are improved in delicacy of hue, and are brought well up among the
leaves, by preventing access of light except to the upper part of the
plants. Of the numerous species of hellebore now grown, the
deep-purple-flowered _H. colchicus_ is one of the handsomest; by
crossing with _H. guttatus_ and other species several valuable garden
forms have been produced, having variously coloured spreading or
bell-shaped flowers, spotted with crimson, red or purple.
The rhizome of _H. niger_ occurs in commerce in irregular and nodular
pieces, from about 1 to 3 in. in length, white and of a horny texture
within. Cut transversely it presents internally a circle of 8 to 12
cuneiform ligneous bundles, surrounded by a thick bark. It emits a faint
odour when cut or broken, and has a bitter and slightly acrid taste. The
drug is sometimes adulterated with the rhizome of baneberry, _Actaea
spicata_, which, however, may be recognized by the distinctly cruciate
appearance of the central portion of the attached roots when cut
across, and by its decoction giving the chemical reactions for
tannin.[1] The rhizome is darker in colour in proportion to its degree
of dryness, age and richness in oil. A specimen dried by Schroff lost in
eleven days 65% of water.
_H. niger_, _orientalis_, _viridis_, _foetidus_, and several other
species of hellebore contain the glucosides _helleborin_, C36H42O6,
and _helleborein_, C23H20O15, the former yielding glucose and
_helleboresin_, C30H38O4, and the latter glucose and a violet-coloured
substance _helleboretin_, C14H20O3. Helleborin is most abundant in _H.
viridis_. A third and volatile principle is probably present in _H.
foetidus_. Both helleborin and helleborein act poisonously on animals,
but their decomposition-products helleboresin and helleboretin seem to
be devoid of any injurious qualities. Helleborin produces excitement
and restlessness, followed by paralysis of the lower extremities or
whole body, quickened respiration, swelling and injection of the
mucous membranes, dilatation of the pupil, and, as with helleborein,
salivation, vomiting and diarrhoea. Helleborein exercises on the heart
an action similar to that of digitalis, but more powerful, accompanied
by at first quickened and then slow and laboured respiration; it
irritates the conjunctiva, and acts as a sternutatory, but less
violently than veratrine. Pliny states that horses, oxen and swine are
killed by eating "black hellebore"; and Christison (_On Poisons_, p.
876, 11th ed., 1845) writes: "I have known severe griping produced by
merely tasting the fresh root in January." Poisonous doses of
hellebore occasion in man singing in the ears, vertigo, stupor,
thirst, with a feeling of suffocation, swelling of the tongue and
fauces, emesis and catharsis, slowing of the pulse, and finally
collapse and death from cardiac paralysis. Inspection after death
reveals much inflammation of the stomach and intestines, more
especially the rectum. The drug has been observed to exercise a
cumulative action. Its extract was an ingredient in Bacher's pills, an
empirical remedy once in great repute in France. In British medicine
the rhizome was formerly official. _H. foetidus_ was in past times
much extolled as an anthelmintic, and is recommended by Bisset (_Med.
Ess._, pp. 169 and 195, 1766) as the best vermifuge for children; J.
Cook, however, remarks of it (_Oxford Mag._, March 1769, p. 99):
"Where it killed not the patient, it would certainly kill the worms;
but the worst of it is, it will sometimes kill both." This plant, of
old termed by farriers ox-heel, setter-wort and setter-grass, as well
as _H. viridis_ (Fr. _Herbe a seton_), is employed in veterinary
surgery, to which also the use of _H. niger_ is now chiefly confined
in Britain.
In the early days of medicine two kinds of hellebore were recognized,
the white or _Veratrum album_ (see VERATRUM), and the black, including
the various species of _Helleborus_. The former, according to
Codronchius (_Comm.... de elleb._, 1610), Castellus (_De helleb.
epist._, 1622), and others, is the drug usually signified in the
writings of Hippocrates. Among the hellebores indigenous to Greece and
Asia Minor, _H. orientalis_, the rhizome of which differs from that of
_H. niger_ and of _H. viridis_ in the bark being readily separable
from the woody axis, is the species found by Schroff to answer best to
the descriptions given by the ancients of black hellebore, the [Greek:
helleboros melas] of Dioscorides. The rhizome of this plant, if
identical, as would appear, with that obtained by Tournefort at Prusa
in Asia Minor (_Rel. d'un voy. du Levant_, ii. 189, 1718), must be a
remedy of no small toxic properties. According to an early tradition,
black hellebore administered by the soothsayer and physician Melampus
(whence its name _Melampodium_), was the means of curing the madness
of the daughters of Proetus, king of Argos. The drug was used by the
ancients in paralysis, gout and other diseases, more particularly in
insanity, a fact frequently alluded to by classical writers, e.g.
Horace (_Sat._ ii. 3. 80-83, _Ep. ad Pis._ 300). Various superstitions
were in olden times connected with the cutting of black hellebore. The
best is said by Pliny (_Nat. hist._ xxv. 21) to grow on Mt Helicon. Of
the three Anticyras that in Phocis was the most famed for its
hellebore, which, being there used combined with "sesamoides," was,
according to Pliny, taken with more safety than elsewhere.
The British Pharmaceutical Conference has recommended the preparation
which it terms _the tinctura veratri viridis_, as the best form in which
to administer this drug. It may be given in doses of 5-15 minims. The
tincture is prepared from the dried rhizome and rootlets of green
hellebore, containing the alkaloids jervine, veratrine and veratroidine.
It is recommended as a cardiac and nervous sedative in cerebral
haemorrhage and puerperal eclampsia. Black hellebore is a purgative and
uterine stimulant.