[1] The chronology of Hadrian's journeys--indeed, of the whole
reign--is confused and obscure. In the above the article by von
Rohden in Pauly-Wissowa's _Realencyclopadie_ has been followed.
Weber's (see Bibliog.) is the most important discussion.
HADRIAN'S WALL, the name usually given to the remains of the Roman
fortifications which defended the northern frontier of the Roman
province of Britain, between the Tyne and the Solway. The works
consisted of (1) a continuous defensive rampart with a ditch in front
and a road behind; (2) various forts, blockhouses and towers along the
rampart; and (3) an earthwork to the south of it, generally called the
Vallum, of uncertain use. The defensive wall was probably first erected
by Hadrian about A.D. 122 as a turf wall, and rebuilt in stone by
Septimius Severus about A.D. 208. See further BRITAIN: _Roman_.
HADRUMETUM, a town of ancient Africa on the southern extremity of the
_sinus Neapolitanus_ (mod. Gulf of Hammamet) on the east coast of
Tunisia. The site is partly occupied by the modern town of Susa (q.v.).
The form of the name Hadrumetum varied much in antiquity; the Greeks
called it [Greek: Adrymes, Adrymetos, Adramytes, Adrametos]: the Romans
_Adrumetum_, _Adrimetum_, _Hadrumetum_, _Hadrymetum_, &c.; inscriptions
and coins gave _Hadrumetum_. The town was originally a Phoenician colony
founded by Tyrians long before Carthage (Sallust, _Jug._ 19). It became
subject to Carthage, but lost none of its prosperity. Often mentioned
during the Punic Wars, it was captured by Agathocles in 310, and was the
refuge of Hannibal and the remnants of his army after the battle of Zama
in 202. During the last Punic War it gave assistance to the Romans;
after the fall of Carthage in 146 it received an accession of territory
and the title of _civitas libera_ (Appian, _Punica_, xciv.; _C.I.L._ i.
p. 84). Caesar landed there in 46 B.C. on his way to the victory of
Thapsus (_De bello Afric._ iii.; Suetonius, _Div. Jul._ lix.).
In the organization of the African provinces Hadrumetum became a capital
of the province of Byzacena. Its harbour was extremely busy and the
surrounding country unusually fertile. Trajan made it a Latin colony
under the title of _Colonia Concordia Ulpia Trajana Augusta Frugifera
Hadrumetina_; a dedication to the emperor Gordian the Good, found by M.
Cagnat at Susa in 1883 gives these titles to the town, and at the same
time identifies it with Susa. Quarrels arose between Hadrumetum and its
neighbour Thysdrus in connexion with the temple of Minerva situated on
the borders of their respective territories (Frontinus, _Gromatici_, ed.
Lachmannus, p. 57); Vespasian when pro-consul of Africa had to repress
a sedition among its inhabitants (Suetonius, _Vesp._ iv.; Tissot,
_Fastes de la prov. d'Afrique_, p. 66); it was the birthplace of the
emperor Albinus. At this period the metropolis of Byzacena was after
Carthage the most important town in Roman Africa. It was the seat of a
bishopric, and its bishops are mentioned at the councils of 258, 348,
393 and even later. Destroyed by the Vandals in 434 it was rebuilt by
Justinian and renamed Justinianopolis (Procop. _De aedif._ vi. 6). The
Arabic invasion at the end of the 7th century destroyed the Byzantine
towns, and the place became the haunt of pirates, protected by the
Kasbah (citadel); it was built on the substructions of the Punic, Roman
and Byzantine acropolis, and is used by the French for military
purposes. The Arabic geographer Bakri gave a description of the chief
Roman buildings which were standing in his time (Bakri, _Descr. de
l'Afrique_, tr. by de Slane, p. 83 et seq.). The modern town of Susa,
despite its commercial prosperity, occupies only a third of the old
site.
In 1863 the French engineer, A. Daux, discovered the jetties and the
moles of the commercial harbour, and the line of the military harbour
(Cothon); both harbours, which were mainly artificial, are entirely
silted up. There remains a fragment of the fortifications of the Punic
town, which had a total length of 6410 metres, and remains of the
substructions of the Byzantine acropolis, of the circus, the theatre,
the water cisterns, and of other buildings, notably the interesting
Byzantine basilica which is now used as an Arab cafe (Kahwat-el-Kubba).
In the ruins there have been found numerous columns of Punic
inscriptions, Roman inscriptions and mosaic, among which is one
representing Virgil seated, holding the _Aeneid_ in his hand; another
represents the Cretan labyrinth with Theseus and the Minotaur (Heron de
Villefosse, _Revue de l'Afrique francaise_, v., December 1887, pp. 384
and 394; _Comptes rendus de l'Acad. des Inscr. et Belles-Lettres_, 1892,
p. 318; other mosaics, _ibid._, 1896, p. 578; _Revue archeol._, 1897).
In 1904 Dr Carton and the abbe Leynaud discovered huge Christian
catacombs with several miles of subterranean galleries to which access
is obtained by a small vaulted chamber. In these catacombs we find
numerous sarcophagi and inscriptions painted or engraved of the Roman
and Byzantine periods (_Comptes rendus de l'Acad. des Inscr. et
Belles-Lettres_, 1904-1907; Carton and Leynaud, _Les Catacombes
d'Hadrumete_, Susa, 1905). We can recognize also the Punic and
Pagan-Roman cemeteries (_C. R. de l'Acad. des Inscr. et Belles-Lettres_,
1887; _Bull. archeol. du Comite_, 1885, p. 149; 1903, p. 157). The town
had no Punic coins, but under the Roman domination there were coins from
the time of the Republic. These are of bronze and bear the name of the
city in abbreviations, HADR or HADRVM accompanying the head of Neptune
or the Sun. We find also the names of local duumvirs. Under Augustus the
coins have on the obverse the imperial effigy, and on the reverse the
names and often the effigies of the pro-consuls who governed the
province, P. Quintilius Varus, L. Volusius Saturninus and Q. Fabius
Maximus Africanus. After Augustus the mint was finally closed.
AUTHORITIES.--A. Daux, _Recherches sur l'origine et l'emplacement des
emporia pheniciens dans le Zeugis et le Byzacium_ (Paris, 1869); Ch.
Tissot, _Geographie comparee de la province romaine d'Afrique_, ii. p.
149; Cagnat, _Explorations archeol. en Tunisie_ (2nd and 3rd fasc.,
1885); Lud. Muller, _Numismatique de l'Afrique ancienne_, ii p. 51; M.
Palat, in the _Bulletin arch. du Comite des travaux historiques_
(1885), pp. 121 and 150; _Revue archeologique_ (1884 and 1897);
_Bulletin des antiquites africaines_ (1884 and 1885); _Bulletin de la
Societe archeologique de Sousse_ (first published in 1903); _Atlas
archeol. de Tunisie_ (4th fascicule, with the plan of Hadrumetum).
(E. B.*)
HAECKEL, ERNST HEINRICH (1834- ), German biologist, was born at
Potsdam on the 16th of February 1834. He studied medicine and science at
Wurzburg, Berlin and Vienna, having for his masters such men as Johannes
Muller, R. Virchow and R. A. Kolliker, and in 1857 graduated at Berlin
as M.D. and M.Ch. At the wish of his father he began to practise as a
doctor in that city, but his patients were few in number, one reason
being that he did not wish them to be many, and after a short time he
turned to more congenial pursuits. In 1861, at the instance of Carl
Gegenbaur, he became _Privatdozent_ at Jena; in the succeeding year he
was chosen extraordinary professor of comparative anatomy and director
of the Zoological Institute in the same university; in 1865 he was
appointed to a chair of zoology which was specially established for his
benefit. This last position he retained for 43 years, in spite of
repeated invitations to migrate to more important centres, such as
Strassburg or Vienna, and at Jena he spent his life, with the exception
of the time he devoted to travelling in various parts of the world,
whence in every case he brought back a rich zoological harvest.
As a field naturalist Haeckel displayed extraordinary power and
industry. Among his monographs may be mentioned those on _Radiolaria_
(1862), _Siphonophora_ (1869), _Monera_ (1870) and _Calcareous Sponges_
(1872), as well as several _Challenger_ reports, viz. _Deep-Sea Medusae_
(1881), _Siphonophora_ (1888), _Deep-Sea Keratosa_ (1889) and
_Radiolaria_ (1887), the last being accompanied by 140 plates and
enumerating over four thousand new species. This output of systematic
and descriptive work would alone have constituted a good life's work,
but Haeckel in addition wrote copiously on biological theory. It
happened that just when he was beginning his scientific career Darwin's
_Origin of Species_ was published (1859), and such was the influence it
exercised over him that he became the apostle of Darwinism in Germany.
He was, indeed, the first German biologist to give a whole-hearted
adherence to the doctrine of organic evolution and to treat it as the
cardinal conception of modern biology. It was he who first brought it
prominently before the notice of German men of science in his first
memoir on the _Radiolaria_, which was completely pervaded with its
spirit, and later at the congress of naturalists at Stettin in 1863.
Darwin himself has placed on record the conviction that Haeckel's
enthusiastic propagandism of the doctrine was the chief factor of its
success in Germany. His book on _General Morphology_ (1866), published
when he was only thirty-two years old, was called by Huxley a suggestive
attempt to work out the practical application of evolution to its final
results; and if it does not take rank as a classic, it will at least
stand out as a landmark in the history of biological doctrine in the
19th century. Although it contains a statement of most of the views with
which Haeckel's name is associated, it did not attract much attention on
its first appearance, and accordingly its author rewrote much of its
substance in a more popular style and published it a year or two later
as the _Natural History of Creation (Naturliche Schopfungsgeschichte)_,
which was far more successful. In it he divided morphology into two
sections--tectology, the science of organic individuality; and
promorphology, which aims at establishing a crystallography of organic
forms. Among other matters, he laid particular stress on the
"fundamental biogenetic law" that ontogeny recapitulates phylogeny, that
the individual organism in its development is to a great extent an
epitome of the form-modifications undergone by the successive ancestors
of the species in the course of their historic evolution. His well-known
"gastraea" theory is an outcome of this generalization. He divided the
whole animal creation into two categories--the Protozoa or unicellular
animals, and the Metazoa or multicellular animals, and he pointed out
that while the former remain single-celled throughout their existence,
the latter are only so at the beginning, and are subsequently built up
of innumerable cells, the single primitive egg-cell (_ovum_) being
transformed by cleavage into a globular mass of cells (_morula_), which
first becomes a hollow vesicle and then changes into the _gastrula_. The
simplest multicellular animal he conceived to resemble this gastrula
with its two primary layers, ectoderm and endoderm, and the earliest
hypothetical form of this kind, from which the higher animals might be
supposed to be actually descended, he called the "gastraea." This theory
was first put forward in the memoir on the calcareous sponges, which in
its sub-title was described as an attempt at an analytical solution of
the problem of the origin of species, and was subsequently elaborated in
various _Studies on the Gastraea Theory_ (1873-1884). Haeckel, again,
was the first to attempt to draw up a genealogical tree (_Stammbaum_)
exhibiting the relationship between the various orders of animals with
regard both to one another and their common origin. His earliest attempt
in the _General Morphology_ was succeeded by many others, and his
efforts in this direction may perhaps be held to culminate in the paper
he read before the fourth International Zoological Congress, held at
Cambridge in 1898, when he traced the descent of the human race in
twenty-six stages from organisms like the still-existing _Monera_,
simple structureless masses of protoplasm, and the unicellular
_Protista_, through the chimpanzees and the _Pithecanthropus erectus_,
of which a few fossil bones were discovered in Java in 1894, and which
he held to be undoubtedly an intermediate form connecting primitive man
with the anthropoid apes.
Not content with the study of the doctrine of evolution in its
zoological aspects, Haeckel also applied it to some of the oldest
problems of philosophy and religion. What he termed the integration of
his views on these subjects he published under the title of _Die
Weltratsel_ (1899), which in 1901 appeared in English as _The Riddle of
the Universe_. In this book, adopting an uncompromising monistic
attitude, he asserted the essential unity of organic and inorganic
nature. According to his "carbon-theory," which has been far from
achieving general acceptance, the chemico-physical properties of carbon
in its complex albuminoid compounds are the sole and the mechanical
cause of the specific phenomena of movement which distinguish organic
from inorganic substances, and the first development of living
protoplasm, as seen in the _Monera_, arises from such nitrogenous
carbon-compounds by a process of spontaneous generation. Psychology he
regarded as merely a branch of physiology, and psychical activity as a
group of vital phenomena which depend solely on physiological actions
and material changes taking place in the protoplasm of the organism in
which it is manifested. Every living cell has psychic properties, and
the psychic life of multicellular organisms is the sum-total of the
psychic functions of the cells of which they are composed. Moreover,
just as the highest animals have been evolved from the simplest forms of
life, so the highest faculties of the human mind have been evolved from
the soul of the brute-beasts, and more remotely from the simple
cell-soul of the unicellular Protozoa. As a consequence of these views
Haeckel was led to deny the immortality of the soul, the freedom of the
will, and the existence of a personal God.
Haeckel's literary output was enormous, and at the time of the
celebration of his sixtieth birthday at Jena in 1894 he had produced 42
works with 13,000 pages, besides numerous scientific memoirs. In
addition to the works already mentioned, he wrote _Freie Wissenschaft
und freie Lehre_ (1877) in reply to a speech in which Virchow objected
to the teaching of the doctrine of evolution in schools, on the ground
that it was an unproved hypothesis; _Die systematische Phylogenie_
(1894), which has been pronounced his best book; _Anthropogenie_ (1874,
5th and enlarged edition 1903), dealing with the evolution of man; _Uber
unsere gegenwartige Kenntnis vom Ursprung des Menschen_ (1898,
translated into English as _The Last Link_, 1898); _Der Kampf um den
Entwickelungsgedanken_ (1905, English version, _Last Words on
Evolution_, 1906); _Die Lebenswunder_ (1904), a supplement to the
_Riddle of the Universe_; books of travel, such as _Indische
Reisebriefe_ (1882) and _Aus Insulinde_ (1901), the fruits of journeys
to Ceylon and to Java; _Kunstformen der Natur_ (1904), with plates
representing beautiful marine animal forms; and _Wanderbilder_ (1905),
reproductions of his oil-paintings and water-colour landscapes.
There are biographies by W. Bolsche (Dresden, 1900, translated into
English by Joseph McCabe, with additions, London, 1906) and by
Breitenbach (Odenkirchen, 1904). See also Walther May, _Ernst
Haeckel_; _Versuch einer Chronik seines Lebens und Werkens_ (Leipzig,
1909).
HAEMATITE, or HEMATITE, a mineral consisting of ferric oxide (Fe2O3),
named from the Greek word [Greek: haima] "blood," in allusion to its
typical colour, whence it is called also red iron ore. When
crystallized, however, haematite often presents a dark colour, even
iron-black; but on scratching the surface, the powder of the streak
shows the colour of dried blood. Haematite crystallizes in the
rhombohedral system, and is isomorphous with corundum (Al2O3). The
habit of the crystals may be rhombohedral, pyramidal or tabular, rarely
prismatic. In fig. 1 the crystal, from Elba, shows a combination of the
fundamental rhombohedron (R), an obtuse rhombohedron (s), and the
hexagonal bi-pyramid (n). Fig. 2 is a tabular crystal in which the basal
pinacoid (o) predominates. Haematite has no distinct cleavage, but may
show, in consequence of a lamellar structure, a tendency to parting
along certain planes.
[Illustration: FIG. 1.]
[Illustration: FIG. 2.]
Crystallized haematite, such as that from the iron-mines of Elba,
presents a steel-grey or iron-black colour, with a brilliant metallic
lustre, sometimes beautifully iridescent. The splendent surface has
suggested for this mineral such names as specular iron ore,
looking-glass ore, and iron glance (_fer oligiste_ of French writers).
The hardness of the crystallized haematite is about 6, and the specific
gravity 5.2. The so-called "iron roses" (_Eisenrosen_) of Switzerland
are rosette-like aggregates of hexagonal tabular crystals, from fissures
in the gneissose rocks of the Alps. Specular iron ore occurs in the form
of brilliant metallic scales on many lavas, as at Vesuvius and Etna, in
the Auvergne and the Eifel, and notably in the Island of Ascension,
where the mineral forms beautiful tabular crystals. It seems to be a
sublimation-product formed in volcanoes by the interaction of the vapour
of ferric chloride and steam.
Specular haematite forms a constituent of certain schistose rocks, such
as the Brazilian itabirite. In the Marquette district of Michigan (Lake
Superior) schistose specular ore occurs in important deposits,
associated with a jasper rock, in which the ore alternates with bands of
red quartzite. Micaceous iron ore consists of delicate steel-grey scales
of specular haematite, unctuous to the touch, used as a lubricant and
also as a pigment. It is worked in Devonshire under the name of shining
ore. Very thin laminae of haematite, blood-red by transmitted light,
occur as microscopic enclosures in certain minerals, such as carnallite
and sun-stone, to which they impart colour and lustre.
Much haematite occurs in a compact or massive form, often mammillary,
and presenting on fracture a fibrous structure. The reniform masses are
known as kidney ore. Such red ore is generally neither so dense nor so
hard as the crystals. It often passes into an earthy form, termed soft
red ore, and when mixed with more or less clay constitutes red ochre,
ruddle or reddle (Ger. _Rotel_).
The hard haematite is occasionally cut and polished as an ornamental
stone, and certain kinds have been made into beads simulating black
pearls. It was worked by the Assyrians for their engraved
cylinder-seals, and was used by the gnostics for amulets. Some of the
native tribes in the Congo basin employ it as a material for axes. The
hard fibrous ore of Cumberland is known as pencil ore, and is employed
for the burnishers used by bookbinders and others. Santiago de
Compostela in Spain furnishes a considerable supply of haematite
burnishers.
Haematite is an important ore of iron (q.v.), and is extensively worked
in Elba, Spain (Bilbao), Scandinavia, the Lake Superior region and
elsewhere. In England valuable deposits occur in the Carboniferous
Limestone of west Cumberland (Whitehaven district) and north Lancashire
(Ulverston district). The hard ore is siliceous, and fine crystallized
specimens occur in association with smoky quartz. The ore is remarkably
free from phosphorus, and is consequently valued for the production of
pig-iron to be converted into Bessemer steel. (F. W. R.*)
HAEMATOCELE (Gr. [Greek: haima], blood, and [Greek: kele], tumour), the
medical term for a localized collection of blood in the tunica vaginalis
or cord. It is usually the result of a sudden blow or severe strain, but
may arise from disease. At first it forms a smooth, fluctuating, opaque
swelling, but later becomes hard and firm. In chronic cases the walls of
the tunica vaginalis undergo changes. The treatment of a case seen soon
after the injury is directed towards keeping the patient at rest,
elevating the parts, and applying an evaporating lotion or ice-bag. In
chronic cases it may be necessary to lay open the cavity and remove the
coagulum.
HAEMOPHILIA, the medical term for a condition of the vascular system,
often running in families, the members of which are known as "bleeders,"
characterized by a disposition towards bleeding, whether with or without
the provocation of an injury to the tissue. When this bleeding is
spontaneous it comes from the mucous membranes, especially from the
nose, but also from the mouth, bowel and bronchial tubes. Slight bruises
are apt to be followed by extravasations of blood into the tissues; the
swollen joints (knee especially) of a bleeder are probably due, in the
first instance, to the escape of blood into the joint cavity or synovial
membrane. It is always from the smallest vessels that the blood escapes,
and may do so in such quantities as to cause death in a few hours.
HAEMORRHAGE (Gr. [Greek: haima], blood, and [Greek: rhegnynai], to
burst), a general term for any escape of blood from a blood-vessel (see
Blood). It commonly results from injury, as the tearing or cutting of a
blood-vessel, but certain forms result from disease, as in scurvy and
purpura. The chief varieties of haemorrhage are _arterial_, _venous_ and
_capillary_. Bleeding from an artery is of a bright red colour, and
escapes from the end of the vessel nearest the heart in jets synchronous
with the heart's beat. Bleeding from a vein is of a darker colour; the
flow is steady, and the bleeding is from the distal end of the vessel.
Capillary bleeding is a general oozing from a raw surface. By
_extravasation of blood_ is meant the pouring out of blood into the
areolar tissues, which become boggy. This is termed a _bruise_ or
_ecchymosis_. _Epistaxis_ is a term given to bleeding from the nose.
_Haematemesis_ is vomiting of blood, the colour of which may be altered
by digestion, as is also the case in _melaena_, or passage of blood with
the faeces, in which the blood becomes dark and tarry-looking from the
action of the intestinal fluids. _Haemoptysis_ denotes an escape of
blood from the air-passages, which is usually bright red and frothy from
admixture with air. _Haematuria_ means passage of blood with the urine.
Cessation of bleeding may take place from natural or from artificial
means. Natural arrest of haemorrhage arises from (1) the coagulation of
the blood itself, (2) the diminution of the heart's action as in
fainting, (3) changes taking place in the cut vessel causing its
retraction and contraction. In the surgical treatment of haemorrhage
minor means of arresting bleeding are: cold, which is most valuable in
general oozing and local extravasations; very hot water, 130 deg. to 160
deg. F., a powerful haemostatic; position, such as elevation of the
limb, valuable in bleeding from the extremities; styptics or
astringents, applied locally, as perchloride of iron, tannic acid and
others, the most valuable being suprarenal extract. In arresting
haemorrhage temporarily the chief thing is to press directly on the
bleeding part. The pressure to be effectual need not be severe, but must
be accurately applied. If the bleeding point cannot be reached, the
pressure should be applied to the main artery between the bleeding point
and the heart. In small blood-vessels pressure will be sufficient to
arrest haemorrhage permanently. In large vessels it is usual to pass a
ligature round the vessel and tie it with a reef-knot. Apply the
ligature, if possible, at the bleeding point, tying both ends of the cut
vessel. If this cannot be done, the main artery of the limb must be
exposed by dissection at the most accessible point between the wound and
the heart, and there ligatured.
Haemorrhage has been classified as--(1) primary, occurring at the time
of the injury; (2) reactionary, or within twenty-four hours of the
accident, during the stage of reaction; (3) secondary, occurring at a
later period and caused by faulty application of a ligature or septic
condition of the wound. In severe haemorrhage, as from the division of a
large artery, the patient may collapse and death ensue from syncope. In
this case stimulants and strychnine may be given, but they should be
avoided until it is certain the bleeding has been properly controlled,
as they tend to increase it. Transfusion of blood directly from the
vein of a healthy person to the blood-vessels of the patient, and
infusion of saline solution into a vein, may be practised (see Shock).
In a congenital condition known as _haemophylia_ (q.v.) it is difficult
to stop the flow of blood.
The surgical procedure for the treatment of an open wound is--(1) arrest
of haemorrhage; (2) cleansing of the wound and removal of any foreign
bodies; (3) careful apposition of its edges and surfaces--the edges
being best brought in contact by sutures of aseptic silk or catgut, the
surfaces by carefully applied pressure; (4) free drainage, if necessary,
to prevent accumulation either of blood or serous effusion; (5)
avoidance of sepsis; (6) perfect rest of the part. These methods of
treatment require to be modified for wounds in special situations and
for those in which there is much contusion and laceration. When a
special poison has entered the wound at the time of its infliction or at
some subsequent date, it is necessary to provide against septic
conditions of the wound itself and blood-poisoning of the general
circulation.
HAEMORRHOIDS, or Hemorrhoids (from Gr. [Greek: haima], blood, and [Greek:
rhein], to flow), commonly called _piles_, swellings formed by the
dilatation of veins of the lowest part of the bowel, or of those just
outside the margin of its aperture. The former, _internal piles_, are
covered by mucous membrane; the latter, _external piles_, are just
beneath the skin. As the veins of the lining of the bowel become dilated
they form definite bulgings within the bowel, and, at last increasing in
size, escape through the anus when a motion is being passed. Growing
still larger, they may come down spontaneously when the individual is
standing or walking, and they are apt to be a grave source of pain or
annoyance. Eventually they may remain constantly protruded--nevertheless,
they are still _internal_ piles because they arise from the interior of
the bowel. Though a pile is sometimes solitary, there are usually several
of them. They are apt to become inflamed, and the inflammation is
associated with heat, pain, discharge and general uneasiness; ulceration
and bleeding are also common symptoms, hence the term "bleeding piles."
The _external pile_ is covered by the thin dark-coloured skin of the anal
margin. Severe pressure upon the large abdominal veins may retard the
upward flow of blood to the heart and so give rise to piles; this is apt
to happen in the case of disease of the liver, malignant and other
tumours, and pregnancy. General weakness of the constitution or of the
blood-vessels and habitual constipation may be predisposing causes of
piles. The exciting cause may be vigorous straining at stool or exposure
to damp, as from sitting on the wet ground. Piles are often only a
symptom, and in their treatment this fact should be kept in view; if the
cause is removed the piles may disappear. But in some cases it may be
impossible to remove the cause, as when a widely-spreading cancerous
growth of the rectum, or of the interior of the pelvis or abdomen, is
blocking the upward flow of blood in the veins. Sometimes when a pile has
been protruded, as during defaecation, it is tightly grasped by spasmodic
contraction of the circular muscular fibres which guard the outlet of the
bowel, and it then becomes swollen, engorged and extremely painful; the
strangulation may be so severe that the blood in the vessels coagulates
and the pile mortifies. This, indeed, is nature's attempt at curing a
pile, but it is distressing, and, as a rule, it is not entirely
successful.
The palliative treatment of piles consists in obtaining a daily and easy
action of the bowels, in rest, cold bathing, astringent injections,
lotions and ointments. The radical treatment consists in their removal
by operation, but this should not be contemplated until palliative
treatment has failed. The operation consists in drawing the pile well
down, and strangling the vessels entering and leaving its base, either
by a strong ligature tightly applied, by crushing, or by cautery. Before
dealing with the pile the anus is vigorously dilated in order that the
pile may be dealt with with greater precision, and also that the
temporary paralysis of the sphincter muscle, which follows the
stretching, may prevent the occurrence of painful and spasmodic
contractions subsequently. The ligatures by which the base of the piles
are strangulated slough off with the pile in about ten days, and in
about ten days more the individual is, as a rule, well enough to return
to his work. If, for one reason or another, no operation is to be
undertaken, and the piles are troublesome, relief may be afforded by
warm sponging and by sitz-baths, the pile being gently dried afterwards
by a piece of soft linen, smeared with vaseline, and carefully returned
into the bowel. Under surgical advice, cocaine or morphia may be brought
in contact with the tender parts, either in the form of lotion,
suppository or ointment. In operating upon internal piles it is
undesirable to remove all the external piles around the anus, lest the
contraction of the circumferential scar should cause permanent narrowing
of the orifice. If, as often happens, blood clots in the vein of an
external pile, the small, hard, tender swelling may be treated with
anodyne fomentations, or it may be rendered insensitive by the ether
spray and opened by a small incision, the clot being turned out.
(E. O.*)
HAEMOSPORIDIA, in zoology, an order of Ectospora, which although
comparatively few in number and very inconspicuous in size and
appearance, have of late years probably attracted greater attention and
been more generally studied than any other Sporozoa; the reason being
that they include the organisms well known as malarial parasites. In
spite, however, of much and careful recent research--to a certain
extent, rather, as a result of it--it remains the case that the
Haemosporidia are, in some respects, the group of the Ectospora about
which our knowledge is, for the time being, in the most unsatisfactory
condition. Such important questions, indeed, as the scope and boundaries
of the group, its exact origin and affinities, the rank and
interclassification of the forms admittedly included in it, are answered
quite differently by different workers. For example, one well-known
Sporozoan authority (M. Luhe) has recently united the two groups,
Haemosporidia and Haemoflagellates, bodily into one, while others (e.g.
Novy and McNeal) deny that there is any connexion whatever between
"Cytozoa" and Trypanosomes. Again, the inclusion or exclusion of forms
like _Piroplasma_ and _Halteridium_ is also the subject of much
discussion. The present writer accepts here the view that the
Haemosporidia are derived from Haemoflagellates which have developed a
gregariniform (Sporozoan) phase at the expense, largely or entirely, of
the flagelliform one. The not inconsiderable differences met with among
different types are capable of explanation on the ground that certain
forms have advanced farther than others along this particular line of
evolution. In other words, it is most probable that the Haemosporidia
are to be regarded as comprising various parasites which represent
different stages intermediate between, on the one side, a Flagellate,
and on the other, a typical chlamydospore-forming Ectosporan parasite.
While, however, it is easy enough sharply to separate off all
Haemosporidia from other Ectospora, it is a very difficult matter to
define their limits on the former side. Two principal criteria which a
doubtful haemal parasite might very well be required to satisfy in order
to be considered as a Haemosporidian rather than a Haemoflagellate are
(a) the occurrence of schizogony during the "corpuscular" phase in the
Vertebrate host, and (b) the formation of many germs ("sporozoites")
from the zygote; so long as these conditions were complied with, the
present writer, at all events, would not feel he was countenancing any
protozoological heresy in allowing for the possibility of a Flagellate
(perhaps trypaniform) phase or features being present at some period or
other in the life-cycle.[1] To render this article complete, however,
one or two well-known parasites, hitherto referred to this order, must
also be mentioned, which, judged by the above (arbitrary) standard, are,
it may be, on the Haemoflagellate side of the dividing line (e.g.
_Halteridium_, according to Schaudinn).
The chief characters which distinguish the Haemosporidia from other
Ectospora are the following. They are invariably blood parasites, and
for part or all of the trophic period come into intimate relation with
the cellular elements in the blood. There is always an alternation of
hosts and of generations, an Invertebrate being the definitive host, in
which sexual conjugation is undergone and which is to be regarded as the
primary one, a Vertebrate being the intermediate or secondary one. The
zygote or sporont is at first capable of movement and known as an
ookinete. No resistant spores (chlamydospores) are formed, the ultimate
germs or sporozoites always being free in the oocyst and not enclosed by
sporocysts.
To Sir E. Ray Lankester is due the honour of discovering the first
Haemosporidian, a discovery which did not take place until after most of
the other kinds of Sporozoa were known. In 1871 this author described
the parasite of the frog, which he later termed _Drepanidium ranarum_.
The next discovery was the great and far-reaching one of Laveran, who in
1883 described all the characteristic phases of the malarial parasite
which are met with in human blood. While regarding the organism as the
cause of the disease, Laveran did not at once recognize its animal and
Sporozoan nature, but considered it rather as a vegetable, and termed it
_Oscillaria malariae_. As in the case of the Trypanosomes, we owe to
Danilewsky (1885-1889) the first serious attempts to study the
comparative anatomy and life-history of these parasites, from a
zoological point of view. Danilewsky first named them Haemosporidia, and
distinguished between _Haemocytozoa_ and _Leucocytozoa_. To the
brilliant researches of R. Ross and Grassi in the closing years of the
19th century is due the realization of the essential part played by the
gnat or mosquito in the life-cycle and transmission of the parasites;
and to MacCallum belongs the credit of first observing the true sexual
conjugation, in the case of a _Halteridium_. Since then, thanks to the
labours of Argutinsky and Schaudinn, our knowledge of the malarial
parasites has steadily increased. Until quite recently, however, very
little was known about the Haemosporidia of cold-blooded Vertebrates;
but in 1903 Siegel and Schaudinn demonstrated that the same role is
performed in their case by a leech or a tick, and since then many new
forms have been described.
Occurrence: habitat; effects on host.
The Haemosporidia are widely distributed and of very general occurrence
among the chief classes of Vertebrates. Among Invertebrates they are
apparently limited to bloodsucking insects, ticks and leeches.[2] As
already stated, the universal habitat of the parasites in the Vertebrate
is the blood; as a result, of course, they are to be met with in the
capillaries of practically all the important organs of the body; and it
is to be noted that while certain phases (e.g. growing trophozoites,
mature gametocytes) are found in the peripheral circulation, others
(e.g. schizogonous "rosettes," young gametocytes) occur in the internal
organs, liver, kidneys, &c., where the circulation is sluggish. The
relation of the parasites to the blood-cells varies greatly. Most
attack, probably exclusively, the red blood corpuscles (haematids); a
few, however, select the leucocytes, and are therefore known as
Leucocytozoa. In the case of Mammalian and Avian forms (malarial
parasites) Schaudinn and Argutinsky have shown that the trophic and
schizogonic phases are not really endoglobular but closely attached to
the corpuscle, hollowing out a depression or space into which they
nestle; the gametocytes, on the other hand, are actually intercellular.
Forms parasitic in cold-blooded Vertebrates, on the contrary, are
always, so far as is known, endoglobular when in relation with the
corpuscles; and the same is apparently the case with the Mammalian
parasite, _Piroplasma_. Although in no instance so far described is the
parasite actually intranuclear (as certain Coccidia are), in one or two
cases (e.g. _Karyolysus_ of lizards and certain species of
_Haemogregarina_) it reacts markedly upon the nucleus and soon causes
its disintegration. While many Haemosporidia (e.g. malarial parasites,
with the exception of _Halteridium_) remain in connexion with the same
corpuscle throughout the whole period of growth and schizogony, the new
generation of merozoites first being set free from the broken-down cell,
others (the Haemogregarines, broadly speaking, and also _Halteridium_)
leave one corpuscle after a short time, wander about free in the plasma,
and then seek out another; and this may be repeated until the parasite
is ready for schizogony, which generally occurs in the corpuscle.
As in the case of Trypanosomes (q.v.), normally--that is to say, when in
an accustomed, tolerant host, and under natural conditions--Haemosporidia
are non-pathogenic and do not give rise to any ill-effects in the animals
harbouring them. When, however, the parasites gain an entry into the
blood of man or other unadapted animals,[3] they produce, as is well
known, harmful and often very serious effects. There are three recognized
types of malarial fever, each caused by a distinct form and characterized
by the mode of manifestation. Two, the so-called benign fevers, are
intermittent; namely, tertian and quartan fever, in which the fever
recurs every second and third day respectively. This is due to the fact
that schizogony takes different lengths of time in the two cases, 48
hours in the one, 72 in the other; the height of the fever-period
coincides with the break-down of the corpuscle at the completion of the
process, and the liberation of great numbers of merozoites in the blood.
The third type is the dangerous aestivo-autumnal or pernicious malaria,
in which the fever is irregular or continuous during long periods.
A very general symptom is anaemia, which is sometimes present to a
marked extent, when it may lead to a fatal termination. This is the
result of the very considerable destruction of the blood-corpuscles
which takes place, the haemoglobin of which is absorbed by the parasites
as nutriment. A universal feature connected with this mode of nutrition
is the production, in the cytoplasm of the parasite, of a brown pigment,
termed melanin; this does not represent reserve material, but is an
excreted by-product derived from the haemoglobin. These pigment-grains
are at length liberated into the blood-stream and become deposited in
the various organs, spleen, liver, kidneys, brain, causing pronounced
pigmentation.
Another type of fever, more acute and more generally fatal, is that
produced by forms belonging to the genus _Piroplasma_, in cattle, dogs,
horses and other domestic animals in different regions of the globe; and
recently Wilson and Chowning have stated that the "spotted fever of the
Rockies" is a human piroplasmosis caused by _P. hominis_. The disease of
cattle is known variously as Texas-fever, Tristeza, Red-water, Southern
cattle-fever, &c. In this type of illness the endogenous multiplication
of the parasites is very great and rapid, and brings about an enormous
diminution in the number of healthy red blood corpuscles. Their sudden
destruction results in the liberation of large quantities of haemoglobin
in the plasma, which turns deep-red in colour; and hence
haemoglobinuria, which occurs only rarely in malaria, is a constant
symptom in piroplasmosis.
Example of the life-history.
The parasite of pernicious malaria, here termed _Laverania malariae_,
will serve very well as a type of the general life-cycle (fig. 1).
Slight differences shown by the other malarial parasites (_Plasmodium_)
will be mentioned in passing, but the main divergences which other
Haemosporidian types exhibit are best considered separately. With the
bite of an infected mosquito, the minute sickle-like sporozoites are
injected into the blood. They rapidly penetrate into the blood
corpuscles, in which they appear as small irregular, more or less
amoeboid trophozoites. A vacuole next arises in the cytoplasm, which
increases greatly in size, and gives rise to the well-known, much
discussed ring-form of the parasite, in which it resembles a
signet-ring, the nucleus forming a little thickening to one side. Some
authorities (e.g. Argutinsky) have regarded this structure as being
really a greatly distended vesicular nucleus, and, to a large extent,
indeed, an artifact, resulting from imperfect fixation; but Schaudinn
considers it is a true vacuole, and explains it on the ground of the
rapid nutrition and growth. Later on this vacuole disappears, and the
grains of pigment make their appearance. The trophozoite is now large
and full-grown, and has become rounded and ready for schizogony. The
nucleus of the schizont divides several times (more or less directly, by
simple or multiple fission) to form a number of daughter-nuclei, which
take up a regular position near the periphery. Around these the
cytoplasm becomes segmented, giving rise to the well-known _corps en
rosace_. Eventually the merozoites, in the form of little round
uninuclear bodies, are liberated from the now broken-down corpuscle,
leaving behind a certain amount of residual cytoplasm containing the
pigment grains. Besides the difference in the time taken by the complete
process of schizogony in the various species (see above), there are
distinctions in the composition of the rosettes. Thus, in _Laverania_,
the number of merozoites formed is very variable; in _Plasmodium vivax_
(the tertian parasite) there are only few (9 to 12) merozoites, but in
_P. malariae_ (the quartan form) they are more numerous, from 12 to 24.
The liberated merozoites proceed to infect fresh blood corpuscles and a
new endogenous cycle is started.
After asexual multiplication has gone on for some time, sexual forms
become developed. According to Schaudinn, the stimulus which determines
the production of gametocytes instead of schizonts is the reaction of
the host (at the height of a fever period) upon the parasites. A young
trophozoite which is becoming a gametocyte is distinguished from one
which gives rise to a schizont by its much slower rate of growth, and
the absence of any vacuoles in its cytoplasm. The gametocytes themselves
are characterized by their peculiar shape, like that of a sausage,
whence they are very generally known as "crescents." Male and female
gametocytes are distinguished (roughly) by the arrangement of the
pigment-grains; in the former, they are fairly evenly scattered
throughout the cytoplasm, but in the megagametocytes the pigment tends
to be aggregated centrally, around the nucleus. As they become
full-grown and mature, however, the gametocytes lose their crescentic
form and assume that of an oval, and finally of a sphere. At the same
time, they are set free from the remains of the blood corpuscle. The
spherical stage is practically the limit of development in the
Vertebrate host, although, sometimes, the nucleus of the microgametocyte
may proceed to division. The "crescents" of the pernicious parasite
afford a very important diagnostic difference from the gametocytes of
both species of _Plasmodium_, which have the ordinary, rounded shape of
the schizonts. In the case of the latter, points such as their slower
growth, their less amoeboid character, and their size furnish the means
of distinction.
When a gnat or mosquito sucks blood, all phases of the parasite in the
peripheral circulation at that point may succeed in passing into the
insect. If this occurs all trophic and schizogonic phases are forthwith
digested, and the survival of the sexual phases depends entirely upon
whether the insect is a gnat or mosquito. Only in the latter case can
further development of the gametocytes go on; in other words, only the
genus _Anopheles_, and not the genus _Culex_, furnishes specific hosts
for the malarial parasites. This is a biological fact of considerable
importance in connexion with the prophylactic measures against malaria.
In the stomach of an _Anopheles_, the gametocytes quickly proceed to
gamete-formation. The nucleus of the microgametocyte divides up, and the
daughter-nuclei pass to the periphery. The surface of the body grows out
into long, whip-like processes, of which there are usually 6 to 8
(probably the typical number is 8); each is very motile, in this respect
strongly resembling a flagellum. This phase may also develop in drawn
blood, which has, of course, become suddenly cooled by the exposure; and
it seems evident that it is the change in temperature, from the warm to
the cold-blooded host, which brings about the development of the actual
sexual elements. Earlier observers regarded the phase just described as
representing another parasite altogether, of a Flagellate nature--whence
the well-known term, _Polymitus_-form; and even more recent workers,
such as Labbe who connected it with the malarial parasite, failed to
appreciate its true significance, and considered it rather as a
degeneration-appearance. The micro-gametes soon liberate themselves from
the residual cytoplasm of the parent and swim away in search of a
megagamete; each is a very slender, wavy filament, composed largely of
chromatic substance. The finer details of structure of the microgamete
of a malarial parasite cannot be said, however, to be thoroughly known,
and it is by no means impossible that its structure is really
trypaniform, as, according to Schaudinn's great work, is the case with
the merozoites and sporozoites.
[Illustration: From Lankester's _Treatise on Zoology_.
FIG. 1.--Diagram of the complete life-cycle of the parasite of
pernicious malaria, _Laverania malariae_, Gr. et Fel. The stages on the
upper side of the dotted line are those found in human blood; below the
dotted line are seen the phases through which the parasite passes in the
intermediate host, the mosquito. Plan and arrangement chiefly after
Neveu-Lemaire; details of the figures founded on those of Grassi,
Schaudinn (Leuckart's _Zoologische Wandtafeln_), Ross and others.
I.-V. and 6-10 show the schizogony.
VI.-XII., The sexual generation.
XIII., The motile zygote.
XIV.-XIX., Sporogony.
I.-III., Young amoebulae in blood-corpuscles.
IV., Older, actively amoeboid trophozoite.
V., Still older, less amoeboid trophozoite.
6, Mature schizont.
7, Schizont, with nucleus dividing up.
8, Young rosette stage.
9, Fully formed rosette stage.
10, Merozoites free in the blood by breaking down of the corpuscle.
VI., Young indifferent gametocyte.
VII., a, Male crescent.
VII., b, Female crescent.
VIII., a and b, The gametocytes becoming oval.
IX., a and b, Spherical gametocytes; in the male (IX. a) the nucleus
has divided up.
X., a and b, Formation of gametes; in the male (X. a) the so-called
flagella or male gametes (fl) are thrown out, one of them is seen
detached; in the female (X. b) a portion of the nucleus has been
expelled.
XI., A male gamete penetrating a female gamete at a cone of reception
formed near the nucleus.
XII., Zygote with two pronuclei in proximity.
XIII., Zygote in the motile stage (vermicule or ookinete).
XIV., Encysted zygote (oocyst).
XV., Commencing multiplication of the nuclei in the oocyst.
XVI., Oocyst with numerous sporoblasts.
XVII., Commencing formation of sporozoites.
XVIII., Full-grown oocyst crammed with ripe sporozoites; on one side
the cyst has burst and the sporozoites are escaping.
XIX., Free sporozoites, showing their changes of form.
n, Nucleus of the parasite.
p, Melanin pigment.
fl, "Flagella."
sp. bl., Sporoblasts.
r. n., Residual nuclei.
r. p., Residual protoplasm.]
[Illustration: From Lankester's _Treatise on Zoology_.
FIG. 2.--Stomach of a mosquito, with cysts of Haemosporidia. (After
Ross.)
oes, Oesophagus.
st, Stomach.
cy, Cysts.
Mt, Malpighian tubules.
int, Intestine.]
The megagametocyte becomes a megagamete directly after a process of
maturation, which consists in the expulsion of a certain amount of
nuclear substance. The actual conjugation is quite similar to the
process in Coccidia, and the resulting zygote perfectly homologous. In
the present case, however, the zygote does not at once secrete an
oocyst, with a thick resistant wall; on the contrary, it changes its
shape, and becomes markedly gregariniform and active, and is known for
this reason as an ookinete. The ookinete passes through the epithelial
layer of the stomach, the thinner and more pointed end leading the way,
and comes to rest in the connective tissue forming the outer layer of
the stomach-wall (fig. 2). Here it becomes rounded and cyst-like, and
grows considerably; for only a thin, delicate cyst-membrane is secreted,
which does not impede the absorption of nutriment. Meanwhile, the
nucleus has divided into several, around each of which the cytoplasm
becomes segmented. Each of these segments ("blastophores,"
"zoidophores") is entirely comparable to a sporoblast in the Coccidian
oocyst, the chief difference being that it never forms a spore; moreover
the segments or sporoblasts in the oocyst of a malarial parasite are
irregular in shape and do not become completely separated from one
another, but remain connected by thin cytoplasmic strands. Repeated
multiplication of the sporoblast-nuclei next takes place, with the
result that a great number of little nuclei are found all round the
periphery. A corresponding number of fine cytoplasmic processes grow out
from the surface, each carrying a nucleus with it, and in this manner a
huge number of slender, slightly sickle-shaped germs or sporozoites
("blasts," "zoids," &c.) are formed. Each oocyst may contain from
hundreds to thousands of sporozoites.
When the sporogony (which lasts about 10 days) is completed, the oocyst
ruptures and the sporozoites are set free into the body-cavity, leaving
behind a large quantity of residual cytoplasm, including pigment grains,
&c. The sporozoites are carried about by the blood-stream; ultimately,
however, apparently by virtue of some chemotactic attraction, they
practically all collect in the salivary glands, filling the secretory
cells and also invading the ducts. When the mosquito next bites a man,
numbers of them are injected, together with the minute drop of saliva,
into his blood, where they begin a fresh endogenous cycle.
There is only one other point with regard to the life-history that need
be mentioned. With the lapse of time all trophic and schizogonic
(asexual) phases of the parasite in the blood die off. But it has long
been known that malarial patients, apparently quite cured, may suddenly
exhibit all the symptoms again, without having incurred a fresh
infection. Schaudinn has investigated the cause of this recurrence, and
finds that it is due to the power of the megagametocytes, which are very
resistant and long-lived, to undergo a kind of parthenogenesis under
favourable conditions and give rise to the ordinary asexual schizonts,
which in turn can repopulate the host with all the other phases.
Microgametocytes, on the other hand, die off in time if they cannot pass
into a mosquito.
[Illustration: From Lankester's _Treatise on Zoology_.
FIG. 3.--_Haemogregarina bigemina_, Laveran, from the blood of
blennies. (After Laveran, magnified about 1800 diameters.)
a, The form of the parasite found free in the blood-plasma.
b, Parasite within a blood-corpuscle, preparing for division; the
nucleus has already divided.
c, The parasite has divided into two rounded corpuscles, which
assume the form of the free parasite, as seen in d, e and f.
N, Nucleus of the blood-corpuscle.
n, Nucleus of the parasite. The outline of the blood-corpuscle is
indicated by a thick black line.]
Comparative Morphology; variations in the life-cycle where known.
Various types of form are to be met with among the Haemosporidia. In
one, characteristic of most (though not of absolutely all) parasites
of warm-blooded Vertebrates, the trophozoites are of irregular
amoeboid shape; hence this section is generally known as the
_Haemamoebidae_. In another type, characteristic of the parasites of
cold-blooded Vertebrates, the body possesses a definite, vermiform,
i.e. gregariniform shape, which is retained during the
intracorpuscular as well as during the free condition; this section
comprises the _Haemogregarinidae_. Allied to this latter type of form
are the trophozoites of _Piroplasma_, which are normally pear-shaped;
they differ, however, in being very minute, and, moreover, exhibit
considerable polymorphism, rod-like (so-called bacillary) and
ring-forms being of common occurrence. It is important to note that in
a certain species of _Haemogregarina_ (fig. 3) the young trophozoites
markedly resemble _Piroplasma_ in their pyriform appearance; and a
further point of agreement between the two forms is mentioned below.
Lastly there is the Avian genus _Halteridium_, the trophozoites of
which are characteristically bean-shaped or reniform. True
Haemogregarines also differ in other slight points from "Haemamoebae."
Thus the young endoglobular trophozoite does not exhibit a ring
(vacuolar) phase; and the cytoplasm never contains, at any period, the
characteristic melanin pigment above noted. In some species of
_Haemogregarina_ the parasite, while intracorpuscular, becomes
surrounded by a delicate membrane, the cytocyst; on entering upon an
active, "free" period, the cytocyst is ruptured and left behind with
the remains of the corpuscle. A very interesting cytological feature
is the occurrence, in one or two Haemosporidia, of nuclear dimorphism,
i.e. of a larger and smaller chromatic body, probably comparable to
the trophic and kinetic nuclei of a Trypanosome, or of the
"Leishman-Donovan" bodies. Schaudinn was the first to notice this
character, in _Piroplasma canis_, and his observation has since been
confirmed by Luhe.[4] Moreover, Brumpt has also noticed nuclear
dimorphism in the ookinete of a species of _Haemogregarina_ in a leech
(as the Invertebrate host)--a highly important observation.
As regards the life-history, the endogenous (schizogonous) cycle is
known in many cases. Sometimes schizogony takes the primitive form of
simple binary (probably) longitudinal fission; this is the case in
_Piroplasma_ (fig. 4) and also in _Haemogregarina bigemina_ just
referred to. From this result the pairs of individuals ("twins") so
often found in the corpuscles. In addition, however, at any rate in
_Piroplasma_, it is probable that multiple division (more allied to
ordinary schizogony) also takes place; such is the case, according to
Laveran, in _P. equi_, and the occurrence at times of four parasites
in a corpuscle, arranged in a cruciform manner, is most likely to be
thus explained. Labbe has described schizogony in _Halteridium
danilewskyi_ as taking place in a rather peculiar manner; the parasite
becomes much drawn-out and halter-like, and the actual division is
restricted to its two ends, two clumps of merozoites being formed, at
first connected by a narrow strand of unused cytoplasm, which
subsequently disappears. Some doubt, however, attaches to this
account, as no one else appears to have seen the process. For the
rest, schizogony takes place more or less in the customary way,
allowing for variations in the mode of arrangement of the merozoites.
It remains to be noted that in _Karyolysus lacertarum_, according to
Labbe, two kinds of schizont are developed, which give rise,
respectively, to micromerozoites and megamerozoites, in either case
enclosed in a delicate cytocyst. This probably corresponds to an early
sexual differentiation (such as is found among certain Coccidia
(q.v.), the micromerozoites producing eventually micro-gametocytes,
the others megagametocytes.
[Illustration: From Lankester's _Treatise on Zoology_.
FIG. 4.--Development and schizogony of _Piroplasma bigeminum_ in the
blood-corpuscles of the ox. (After Laveran and Nicolle.)
a, Youngest form.
b, Slightly older.
c and d. Division of the nucleus.
e and f, Division of the body of the parasite.
g, h, i, j, Various forms of the twin parasite.
k and l, Doubly infected corpuscles.]
It has now been recognized for some time that the sexual (exogenous)
part of the life-cycle of all the _Haemamoebidae_ takes place in an
Invertebrate (Insectan) host, and is fundamentally similar to that
above described in those cases where it has been followed. In
contradistinction to the malarial parasites, this host, in the Avian
forms (_Haemoproteus_ and _Halteridium_)[5] is a species of _Culex_
and not of _Anopheles_; in other words, gamete-formation, conjugation
and subsequent sporozoite-formation in these cases will only go on in
the former. On the other hand, in the case of the Haemogregarines, it
was thought until quite lately that the entire life-history, including
conjugation and sporogony, went on in the Vertebrate host; and only in
1902 Hintze described what purported to be the complete life-history
of _Lankesterella (Drepanidium) ranarum_ undergone in the frog. This
view was rendered obsolete by the work of Siegel and Schaudinn, who
demonstrated the occurrence of an alternation of hosts and of
generations in the case of _Haemogregarina stepanovi_, parasitic in a
tortoise, and in _Karyolysus lacertarum_; the Invertebrate hosts, in
which, in both cases, the sexual process is undergone, being
respectively a leech (_Placobdella_) and a tick (_Ixodes_). With this
discovery the main distinction (as supposed) between the Haemosporidia
of warm and of cold-blooded Vertebrates vanished. It was further
acknowledged by Schaudinn (under whom Hintze had worked) that the
latter had been misled by Coccidian cysts and spores, which he took
for those of _Lankesterella_. The gametogony and sporogony of
_Haemogregarina stepanovi_ in the leech agree in essential particulars
with the process above described. The microgametes are extremely
minute, and the sporozoites, which are developed in the salivary
glands, where the motile ookinetes finally come to rest, are extremely
"spirochaetiform"--the full significance of this latter fact being,
perhaps, not appreciated.
Christophers recently described some remarkable phases which he
regarded as belonging to the cycle of _Haemogregarina gerbilli_ (one
of the few Mammalian Haemogregarines known) in a louse
(_Haematopinus_). In a private communication, however, the author
states that he has probably mistaken phases in the development of an
ordinary gregarine parasite in the louse for part of the life-cycle of
this Haemogregarine.
The Mammalian parasite _Piroplasma_ is the one about whose
life-history our knowledge is most vague. Besides the typical and
generally occurring forms, others have also been observed in the
blood, but it is doubtful how far these are to be looked upon as
normal; for instance, Bowhill and Le Doux have described, in various
species, a phase in which a long, slender pseudopodial-like outgrowth
is present, with a swelling at the distal end. It is, moreover, quite
uncertain which are the sexual forms, comparable to gametocytes.
Doflein regards large pear-shaped forms as such (megagametocytes?),
which become spherical when maturing; and Nocard and Motas have
figured amoeboid, irregular forms, with the nucleus fragmented and
possessing flagella-like processes (possibly microgametes?). The
Invertebrate host is well known to be, in the case of all species, a
tick; thus bovine piroplasmosis (_P. bigeminum_) in America is
conveyed by _Rhipicephalus annulatus_ (_Boophilus bovis_), canine
piroplasmosis (_P. canis_) in South Africa by _Haemaphysalis leachi_
(and perhaps _Dermacentor reticulatus_), and so on. The manner in
which the infection is transmitted by the tick varies greatly. In some
cases (e.g. _P. bigeminum_ and _P. canis_) only the generation
subsequent to that which receives the infection (by feeding on an
infected ox) can transmit it back again to another ox; in other words,
true hereditary infection of the ova in the mother-tick is found to
occur. The actual period in the life of the daughter-tick at which it
can convey the infection apparently varies. On the other hand, in the
case of East African coast-fever, Theiler found that hereditary
infection does not occur, the same generation transmitting the
parasite (_P. parvum_) at different periods of life. Little is
certainly known regarding the phases of the parasite which are passed
through in the tick. Lignieres has observed a kind of multiple fission
in the stomach, several very minute bodies, consisting mostly of
chromatin, being formed, which may serve for endogenous reproduction.
Koch has published an account of certain curious forms of _P.
bigeminum_, in which the body is produced into many stiff, ray-like
processes, giving the appearance of a star; according to him fusion of
such forms takes place, and the resulting zygote becomes rounded,
perhaps transitional to the pear-shaped forms.
Classification.
The classification and nomenclature of the Haemosporidia are in a very
unsettled condition. For an account of the various systems and
modifications hitherto adopted, the article of Minchin (see under
SPOROZOA: _Bibliography_) should be consulted. With the realization
that the life-history in the case of the "Haemamoebae" and the
Haemogregarines is fundamentally similar in type, the chief reason for
grouping them as distinct suborders has disappeared. It is most
convenient to regard them as separate, but closely allied families,
the _Plasmodidae_ ("_Haemamoebidae_") and the _Haemogregarinidae_. The
_Piroplasmata_, on the other hand, constitute another family, which is
better placed in a distinct section or sub-order. In addition there
are, as already noted, two or three genera whose systematic position
must be considered as quite uncertain. One is the well-known
_Halteridium_ of Labbe, parasitic in various birds; the type-species
is _H. danilewskyi_ (Gt. and Fel.). Another is the much-debated
parasite of white blood-corpuscles (leucocytes), originally described
in birds by Danilewsky under the name of _Leucocytozoon_, a form of
which has been recently observed in Mammals.
In conclusion, the chief members of the above-mentioned families may
be enumerated.
Fam. _Plasmodidae_ ("_Haemamoebidae_").
Genus _Laverania_, Gr. and Fel. (syn. _Haemamoenas_, Ross), for L.
_malariae_, Gr. and Fel. (synn. L. s. _Plasmodium_, s. "_Haemamoeba_,"
&c., _praecox_ s. _immaculatum_, &c.), the parasite of pernicious
malaria. Genus _Plasmodium_, March. and Celli (syn. "_Haemamoeba_")
for _P. vivax_ and _P. malariae_, the tertian and quartan parasite,
respectively. There is also a form known in apes, _P. kochi_. Genus
_Haemoproteus_, Kruse (syn. _Proteosoma_), for _H. danilewskyi_ (syn.
_Proteosoma grassi_, _Plasmodium praecox_, &c.), parasitic in numerous
birds. Recently, another form has been described, from reptiles, which
Castellani and Willey have termed _Haemocystidium simondi_.
_Remarks._--The distinguishing characters of the malarial parasites
have been mentioned above. Some authorities would include _Laverania_
in the genus _Plasmodium_, as differing only specifically from the
other two forms. It has, moreover, been suggested by Sergent that all
three are merely different phases of the same parasite, predominating
at different seasons; this idea cannot be regarded, however, as in any
way proved so far. From what is known of the morphology and mode of
manifestation of these forms, the differences between _Laverania_ and
the two species of _Plasmodium_ are considerably more pronounced than
those between _P. vivax_ and _P. malariae_; if the latter are to be
considered as distinct species, the first-named is probably
generically distinct. Luhe, it may be noted, in his recent
comprehensive account of the Haematozoa, also takes this view. Lastly,
whatever be the correct solution of the above problem, there is
certainly not sufficient justification for including the Avian genus
_Haemoproteus_, as also only a species of _Plasmodium_, which is done
by some. Its different Vertebrate habitat, and also the fact that its
Insectan definitive host is Culex and not _Anopheles_, differentiate
it sharply from _Laverania_ and _Plasmodium_.
[Illustration: From Lankester's _Treatise on Zoology_.
FIG. 5.--_Haemoproteus danilewskyi_, Kruse (parasite of various
birds). X about 1200. a, b, c and d from the chaffinch; d and e from
the lark. (After Labbe.)
a, Young trophozoite in a blood-corpuscle,
b and c, Older trophozoite.
d and e, Sporulation.
d, Precocious sporulation with few merozoites.
e, Sporulation of a full-grown schizont, with numerous merozoites.
f, Gametocyte.
N, Nucleus of blood-corpuscle.
n, Nucleus of parasite.
p, Pigment.
mz, Merozoites.
r.p, Residual protoplasm.]
[Illustration: From Lankester's _Treatise on Zoology_.
FIG. 6.--_Haemogregarina stepanovi_, Danilewsky (par. _Emys_ and
_Cistudo_), phases of the schizogony. (a-e and j after Laveran; f-i
after Borner.) X 1000 to 1200 diameters.
a, Blood-corpuscle with young trophozoite.
b, Older trophozoite.
c, Full-grown trophozoite, ready to leave the corpuscle.
d and e, Trophozoites free in the blood-plasma, showing changes of
form.
f-i, Trophozoites, still within the blood-corpuscle (not drawn),
showing the structure of the nucleus, the coarse chromatoid
granules in the protoplasm and the manner in which the parasite
grows into the U-shaped Haemogregarine without increase of
body-mass.
j, Commencement of sporulation; the nucleus has divided into eight
nuclei, and the body of the parasite is beginning to divide up
into as many merozoites within a blood-corpuscle.
N, Nucleus of the blood-corpuscle.
n, Nucleus of the parasite.]
Fam. _Haemogregarinidae._--The different genera are characterized
chiefly by their size relative to the blood-corpuscles, and their
disposition in the latter. Here, again, it has been suggested to unite
the various types all in one genus, _Haemogregarina_, but this seems
at least premature when it is remembered how little is known in most
cases of the life-cycle, which may prove to exhibit important
divergences.
Genus _Haemogregarina_, Danilewsky (syn. _Danilewskya_, Labbe). The
body of the parasite exceeds the blood-corpuscle in length, when
adult, and is bent upon itself, like a U. A very great number of
species are known, mostly from reptiles and fishes; among them may be
mentioned _H. stepanovi_ (fig. 6), from _Emys_ and _Cistudo_, whose
sexual-cycle in a leech has been worked out by Siegel (see above), _H.
delagei_, from _Raja_, _H. bigemina_, from blennies, and _H. simondi_,
from soles. Recently one or two Mammalian forms have been observed,
_H. gerbilli_, from an Indian rat (_Gerbillus_), and _H. jaculi_, from
the jerboa.
Genus _Lankesterella_, Labbe (syn. _Drepanidium_, Lankester). The
parasite is not more than three-quarters the length of the corpuscle.
_L. ranarum_ from _Rana_ is the type-species; another, recently
described by Fantham, is _L. tritonis_, from the newt.
[Illustration: From Lankester's _Treatise on Zoology_.
FIG. 7.--_Karyolysus lacertarum_ (Danil.), in the blood-corpuscles of
Lacerta muralis, showing the effects of the parasite upon the nucleus
of the corpuscle. In c and d the nucleus is broken up. N, Nucleus of
the corpuscle; n, nucleus of the parasite, seen as a number of masses
of chromatin, not enclosed by a distinct membrane. (After Marceau.)]
Genus _Karyolysus_, Labbe. The parasite does not exceed the corpuscle
in length; the forms included in this genus, moreover, although not
actually intranuclear, have a marked karyolytic and disintegrating
action upon the nucleus of the corpuscle. The type-species is the
well-known _K. lacertarum_, of lizards; another is _K.
(Haemogregarina) viperini_, from _Tropidonotus_.
In the section of the _Piroplasmata_ there is only the genus
_Piroplasma_, Patton (synn. _Babesia_, Starcovici, _Pyrosoma_, Smith
and Kilborne), the principal species of which are as follows: _P.
bigeminum_, the cause of Texas cattle-fever, tick-fever
(Rinder-malaria) of South Africa, and _P. bovis_, causing
haemoglobinuria of cattle in Southern Europe; there is some
uncertainty as to whether these two are really distinct; _P. canis_,
_P. ovis_ and _P. equi_ associated, respectively, with those animals.
Lately, a very small form, _P. parvum_, has been described by Theiler
in Rhodesia, which causes East-African coast-fever; and another, _P.
muris_, has been observed in white rats by Fantham.
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