Chapter XXIII: Appendix: “Rhizopods in Poliomyelitis acuta.” (17)

_Development._--Several authors (Gros, Schubart, Richter, Leuckart and Davaine) have demonstrated that the ova of Ascaris develop in water or moist earth after a long period of incubation. Freezing and desiccation (if not too long) do not injure their powers of development; the duration of the development depends on the degree of the surrounding temperature. At a medium temperature, after a varying period of incubation, it takes from thirty to forty days for the embryo to become formed. The spirally rolled up embryo, with its so-called “tooth,” formed by three papillæ close together, never leaves the egg-shell in the open, even if the eggs are kept for years under favourable conditions. Davaine proved that the larvæ hatch out in the intestine of the rat, but are again expelled with the fæces; he therefore concluded that the hatching likewise takes place within the intestine of man, but is followed by the invasion of the larvæ. In the meantime Leuckart had sought to infect himself by swallowing embryo-containing eggs, but without results; he therefore conjectured that there must be an intermediary host, and v. Linstow thought he had found it in myriapods (_Julus guttulatus_). Subsequently, Davaine’s opinion proved correct. First of all Grassi succeeded in infecting himself by swallowing 100 embryo-containing eggs of _Ascaris lumbricoides_; five weeks after ingestion the worms had attained maturity and their ova appeared in the fæces. Calandruccio also sought to infect himself, but failed, yet he succeeded in infecting a little boy aged 7. Lutz also reports a successful experiment which must have been positive, as young worms 5·5 to 18 mm. long were expelled. Lutz proved that the eggs lost their albuminous shell by long lying in water and then died when introduced into the stomach; this would explain the failure of Leuckart’s experiment; in moist earth the albuminous shell is retained. Finally, Epstein conducted unimpeachable experiments on three children which place direct infection with embryo-containing eggs beyond doubt; he, moreover, proved that the development of the eggs takes place more rapidly in the fæces when there is free admission of air, sun, and a sufficiency of moisture.

Accordingly, infection occurs partly through water, but principally direct from the soil.

*Ascaris*, sp.

Wellmann states that yet another species of Ascaris in man occurs in the highlands of Angola: up to the present nothing certain is known about it (Welland, “Critical Notes on Tropical Diseases of the Angola Highlands,” _New York Med. Journ. and Philadelphia Med. Journ._, August 12 to September 2, 1905.)

*Ascaris texana*, Smith et Goeth, 1914.

Female alone known; 58 to 60 mm. and upwards in length; characterized by the serration of the anterior border of the lip and by the appearance of interlabia. Evacuated by a white settler in Texas. Position of this worm doubtful.

*Ascaris maritima*, Leuckart, 1876.

Only one immature specimen, a female (43 mm. in length and 1 mm. in breadth), has hitherto been described, and it was vomited by a child in North Greenland in 1865. (R. Leuckart, “Die menschlichen Parasiten,” 1876, edition 2, i, p. 877.)

Genus. *Toxascaris* (τόξον, an arrow), Leiper, 1907.

Body anteriorly bent dorsally, cuticle finely striated. Œsophagus without a distinct bulb. Tail of male tapers to a point. Testis in anterior portion of posterior half of body. Vulva about middle of body. Eggs oval and smooth.

*Toxascaris limbata*, Railliet and Henry, 1911.

Syn.: _Lumbricus canis_, Werner, 1782; _Ascaris teres_, Goeze, 1782;
_Ascaris cati_ et _caniculæ_, Schrank, 1788; _Ascaris canis_ et
_felis_, Gmelin, 1789; _Ascaris tricuspidata_ et _felis_, Bruguiere,
1791; _Ascaris werneri_, Rud., 1793; _Fusaria mystax_, Zeder, 1800;
_Ascaris marginata_ et _mystax_, Rud., 1802; _Ascaris alata_,
Bellingham, 1839.

Striations 6 µ to 12 µ apart. Cephalic wings long, narrow, semi-lanceolate. Male, 4 to 6 cm. Spicules, 1,002 µ and 1,005 µ. Female, 0·5 to 10 cm. Eggs, 75 µ to 85 µ, shell thick and smooth. Host: dog, occasionally man.

Genus. *Belascaris* (Βέλος, an arrow), Leiper, 1907.

Body anteriorly bent ventrally, cuticle coarsely striated. Œsophagus with a distinct bulb. Tail of male conical. A papillæ-bearing protuberance behind the anus. Testis in anterior half of body. Vulva in anterior part of body. Eggs corrugated.

*Belascaris cati*, Schrank, 1788.

Syn.: _Belascaris mystax_, Leiper, 1907; _Ascaris mystax_.

Striations 12 µ to 16 µ apart. Cephalic wings lanceolate. Male 3 to 6 cm. Spicules 17 to 1·9 mm. Female 4 to 10 cm. Eggs, 65 µ to 75 µ in diameter, surface finely honeycombed. Host: domestic cat, and man, eight or nine cases.

*Belascaris marginata*, Rudolphi, 1802.

Striations 16 µ to 22 µ apart. Cephalic wings long, narrow, semi-lanceolate. Male, 5 to 10 cm. Spicules, 750 µ and 950 µ. Female, 9 to 18 cm. Eggs, 75 µ to 80 µ. Shell finely honeycombed. Host: dog.

Genus. *Lagocheilascaris*, Leiper, 1909.

Thick lips separated by a furrow from the body; between the lips small intermediate lips without “pulp.” The cutting angle of each lip bifurcated. Along each lateral line a cuticular wing extending the whole length of the body. Eggs, thick shell with a mosaic pattern.

*Lagocheilascaris minor*, Leiper, 1909.

Male, 9 mm., tail sharply curved. Spicules colourless, 3·5 and 4 mm. long. More than twenty-four pairs of pre-anal papillæ, at least five pairs of post-anal. Female, 15 mm. Straight posteriorly. Vulva 6 mm. from head with two lips. Eggs, 65 µ in diameter. Host: man, cutaneous abscesses. Trinidad.

Family. *Oxyuridæ.*

Genus. *Oxyuris*, Rudolphi, 1803.

Mouth unarmed. The three labial papillæ are only slightly
protuberant, the œsophagus is long and presents two well-marked
bulbs. The vulva is in the anterior part of the body.

*Oxyuris vermicularis*, Linnæus, 1767.

Syn.: _Ascaris vermicularis_, L.; _Fusaria_, Zeder, 1803.

Colour white, the striated cuticle forms projections at the anterior end which extend some distance back along the middle of the ventral and dorsal surfaces; the longitudinal lateral flanges of the skin corresponding to the lateral lines are well seen in transverse sections; there are three small retractile labial papillæ around the mouth. The male measures 3 to 5 mm. in length, and shortens on death; the posterior extremity of the body is curved ventrally and presents six papillæ. Spicule 70 µ long, hook-like. The female is 10 mm. in length and 0·6 mm. in diameter; the anus is about 2 mm. in front of the tip of the tail; the vulva is in the anterior third of the body; the eggs are oval, asymmetrical, with double-contoured shells, and measure 50 µ to 55 µ by 16 µ to 25 µ; they are deposited with clear, non-granular tadpole-like embryos already developed.

_Habitat._--Adults in large intestine of man. Young forms in small intestine and often in the appendix.

The worm lives in the lower part of the small intestine, cæcum and
vermiform appendix, and before becoming adult undergoes two or three
moults (Heller). According to Wagener the worms at times live in the
gut wall, giving rise to calcareous nodules. When the uterus of the
fertilized females begins to fill with eggs they leave the cæcum and
travel through the colon to the rectum. The uterus is now packed with
eggs which contain a tadpole-shaped embryo. Egg-laying now takes
place, partly in the rectum, partly outside, the mode of exit being
not only passive through defecation but also an active one on the
part of the worms when the patient is in bed. In this case the worms
crawl out of the anus, producing a most intolerable itching as they
scatter their eggs between the nates and the perinæum. From here
in the case of girls they may get occasionally into the vulva and
vagina, and even into the oviducts and so into the body cavity. The
worms also may wander through the alimentary canal in the opposite
direction, getting out occasionally through the mouth. Recently a
_rôle_ has been assigned to them, as to other gut parasites, in
appendicitis and typhlitis.

It is stated that the males die after fertilizing the females,
thus explaining why they are so rarely met with in fæces [but
it is probable that they often escape notice from their small
size.--J. W. W. S.].

_Development._--The eggs, which often adhere together, contain a tadpole-like embryo, the thin tail of which is bent upwards ventrally; the embryo in a short time, given a sufficiently high temperature, passes into a second folded nematode-like embryonal stage, lying in the egg-shell, either in the fæces, with which also numerous females pass out, or in the moisture of the groove between the buttocks, and they there await the opportunity of being reintroduced into man _per os_. It is very improbable that infection takes place directly in the large intestine, as is occasionally stated, because although the harbourers of Oxyuris are frequently liable to auto-infection, this takes place exclusively through the mouth, and is conveyed by the fingers, on which the ova of Oxyuris, and occasionally the female worms, have clung.

The opportunity for this is afforded every evening, as naturally the
troublesome itching caused by the wandering of the worms is met by
scratching and rubbing with the fingers. It is therefore possible
that the eggs may even thus be introduced into the nose, where the
young Oxyuris are perhaps hatched out, if they get high enough up on
the moist pituitary mucous membrane. As a matter of fact, the larvæ
of Oxyuris have been found in the nose. Moreover, one can understand
that the eggs of Oxyuris are transferred from person to person by
the hand, directly or indirectly. This again explains the wholesale
infections which occur in collective dwellings, after a person
harbouring Oxyuris has been admitted into boarding-houses, etc. The
primary infection may be also caused in other ways--by foods, fruits,
vegetables and other articles that are eaten raw, and are polluted
with the ova. Perhaps also flies or their excrement play a part in
the distribution of the parasite, similar to that demonstrated by
Grassi as taking place in the spread of the ova of Trichocephalus and
Tænia.

The assumption of a _direct development_ without an intermediary host was first substantiated by Leuckart by experiments on himself and three of his students; about fourteen days after swallowing the eggs the Oxyuris has attained 6 to 7 mm. in length; Grassi, and later on Calandruccio, infected themselves by swallowing adult female Oxyuris, with the same results. Heller found worms in the gut (appendix vermiformis) of a male child five weeks old.

Other species are: _O. compar_ in the cat; _O. curvula_ and _O.
mastigodes_ in horse, ass, mule; _O. ambigua_ in the rabbit; _O.
poculum_ in the horse; _O. tenuicauda_ in the horse. Many species
occur in insects, especially in _Blattidæ_ and _Hydrophilidæ_
(aquatic beetles).

Family. *Mermithidæ.*

Genus. *Mermis*, Dujardin, 1845.

With characters of the family.

*Mermis hominis oris*, Leidy, 1850.

Fourteen centimetres in length, 0·16 mm. in breadth; mouth terminal; posterior extremity obtuse and provided with a recurved hook 50 µ long.

The parasite was “obtained from the mouth of a child.” Stiles
considers it to be probably a Mermis, possibly swallowed in an apple.

*Agamomermis*, Stiles, 1903.

Group name for immature _Mermithidæ_.

*Agamomermis restiformis*, Leidy, 1880.

This worm measures 65 cm. in length, pointed anteriorly, the posterior extremity broadened and rounded off (1·5 mm. in breadth); the mouth is terminal, without lips. Behind the mouth six papillæ; the œsophagus measures 1·125 mm. in length; the intestine appears to terminate blindly.

This parasite was obtained in West Virginia from the urethra of a
young man, aged 20, who for a few days previous to expelling the worm
passed turbid and bloody urine.

TECHNIQUE.

PRESERVATION AND EXAMINATION OF FLUKES.

_Fixation._--(Method A.) (1) Place the flukes in a test tube or small bottle a quarter full of normal saline. Shake the contents _as hard as possible_ (the object of this is to _extend_ the flukes) for half a minute.

(2) Add _immediately_ an equal bulk of saturated aqueous solution of corrosive sublimate and shake again as vigorously as possible for a few minutes.

(3) Transfer when convenient to 70 per cent. alcohol. (Before staining and mounting remove the sublimate with tincture of iodine.)

(Method B.) In case of large flukes, _e.g._, _Fasciola hepatica_, _Fasciolopsis buski_, compress the flukes between two glass slides with rubber bands or thread. Fix in sublimate or in absolute alcohol, or in 10 per cent. formalin.

(Method C.) Place the flukes in 10 per cent. formalin solution.

_Staining_ is successfully effected by using quite _dilute_ solutions of carmine or hæmatein overnight. This is far preferable to using strong solutions, as it may be almost impossible to remove a too intense stain. Almost any dilute carmine solution suffices. One of the best is acetic-alum carmine (boil excess of carmine in a saturated aqueous solution of potash-alum for about fifteen minutes; add glacial acetic acid to the extent of 10 per cent.; let it stand for a week; filter). For use, dilute about thirty times with water. Place the flukes directly in the stain. Stain overnight or longer.

_Differentiation._--In order to get the sharpest picture, it is best now to differentiate (but this may often be omitted) with acid alcohol (70 per cent. alcohol 100 parts, HCl 5 drops). Allow to act from one to twenty-four hours, according to the appearance of the flukes. Similarly, in staining with _hæmatoxylin_ solution, dilute twenty to thirty times so that the water is merely tinged with the stain. Differentiate as before. After staining, dehydrate, clear, and mount in balsam if required.

_Clearing and Mounting._--(1) _Carbolic acid_ (carbolic acid 94, water 6) is a very convenient clearing agent. It may be used for stained or unstained specimens. It will clear rapidly without previous dehydration. If it is required to mount a specimen permanently, transfer from carbolic to alcohol, then cedar-wood oil (or xylol, etc.), then balsam.

(2) _Creasote._--Dehydrate the specimen, stained or unstained, transfer to creasote. If it is desired to mount permanently, transfer back to alcohol, then cedar-wood oil, then balsam.

(3) _Cedar-wood Oil._--Preferable to xylol or oil of cloves. Dehydrate the specimen in alcohol. To mount permanently, transfer to balsam.

(4) _Glycerine._--_Vide_ under methods of preservation of ova; to mount permanently, transfer to glycerine jelly; subsequently to harden the jelly, expose to formalin vapour.

Of these media, carbolic acid has the greatest refractive index excepting that of balsam. The latter may, in some cases, render structures too transparent, and it may be advisable to use only glycerine or glycerine jelly.

PRESERVATION OF OVA IN FÆCES, URINE, BILE, ETC.

Heat some 70 per cent. alcohol in a basin to about 60 to 70° C. (until bubbles begin to appear). Add the fæces, etc., in the proportion of one part to about nine of fixative; keep stirring. Allow the sediment to settle. Transfer to a bottle with some fresh 70 per cent. alcohol.

_Transference to Glycerine._--Prepare 5 per cent., 10 per cent., 20 per cent. solutions of glycerine in 70 per cent. alcohol. Pour off the alcohol in the bottle of fæces, etc., and replace by 5 per cent. glycerine solution. Allow to stand an hour or so. Then in the same way replace the 5 per cent. by a 10 per cent. glycerine, and finally by a 20 per cent. glycerine solution. When in this latter expose freely to the air (protecting from dust), so as to allow the alcohol and water to evaporate. Add a few drops of glycerine from time to time till eventually the ova are in pure glycerine. (In a very moist climate it may be necessary to use lime or calcium chloride to dry the air.) To mount permanently transfer some of the sediment to glycerine jelly.

PRESERVATION AND EXAMINATION OF CESTODES.

_Fixation._--(1) _Saturated aqueous corrosive sublimate._--Add to this glacial acetic acid to the extent of 1 per cent. (Note this fixative will dissolve the “calcareous corpuscles”; 10 grammes of sublimate to 160 c.c. of water will give a saturated solution.) Warm the fixative to 70° to 80° C. (Avoid the use of needles.) Use plenty of fixative. Allow to act for a quarter of an hour or so. (_a_) Transfer to 70 per cent. alcohol. (It is advisable to remove the sublimate by the use of Lugol’s solution, or a solution containing tincture of iodine, adding this until the iodine colour is permanent.) Or (_b_) transfer for preservation to 10 per cent. formalin.

Or (2) 10 _per cent. formalin_.--In order to prevent contraction it is advisable to extend the tapeworm and keep it fixed by glass plates, or wind the worm around a wide glass tube or bottle, and then fix it.

Or (3) _fix in hot alcohol_.

_Staining._--As under flukes. It is necessary to sacrifice portions of the tapeworm for this purpose, cutting out, _e.g._, mature segments, so as to study the topography of the genitalia.

_Clearing._--As under flukes. To examine the hooks satisfactorily it is best to cut off the head with a sharp knife and mount. A certain amount of pressure is then advisable in order to view the hooks completely so as to measure them.

PRESERVATION OF OVA IN FÆCES, ETC.

As under flukes.

PRESERVATION AND EXAMINATION OF NEMATODES.

_Fixation._--(1) Thoroughly wash the worms to get rid of mucus, etc., by shaking up in warm saline (or water) till the washings are clean. Then transfer to 70 per cent. alcohol _heated_ to about 70° C. It is absolutely necessary to use _hot_ fixatives in order to _extend_ the worms. If no alcohol or spirit is immediately available, drop the worms into _hot_ water, or saline, and transfer later to 70 per cent. alcohol.

(2) Drop into hot 10 per cent. formalin.

_Clearing._--(1) Carbolic acid, _vide_ p. 471.

(2) Creasote, _vide_ p. 471.

(3) Glycerine, _vide_ p. 472.

_Staining._--In case of quite small Nematodes, _e.g._, _Anguillulidæ_, carmine may be used, but as a rule staining is not advantageous.

_Rolling._--In order to study the mouth parts, or bursa, etc., it is necessary to place the worm in any desired position. This is done as one would roll a penholder along the table by one’s finger placed on top of it. In the case of a worm, one edge of the cover-glass is placed over the worm, the other is supported by a strip of cardboard. By tapping the cover-glass the worm will now revolve as much as required provided it is _round_ and _straight_. In certain cases it may be necessary for this purpose to cut off the head or tail. Roll these separately.

When a suitable position is got, the worm may be fixed in this position by pressure on the cover-glass, so as slightly to flatten it.

_Mounting the Head._--If it is required to get an end view, it is necessary to cut off the head transversely as near the end as possible, and then mount.

_Detection of Eggs_ (Bass and Hall).--Mix the fæces thoroughly with ten times the volume of water. Filter through gauze. Centrifugalize the filtrate. Wash the sediment and centrifugalize. Repeat twice. To sediment add CaCl_{2} solution, sp. gr. 1250. The eggs float to surface. Pour off surface fluid. Dilute to sp. gr. 1050. Centrifugalize. Examine sediment, which contains practically all the eggs in the stool.

_Detection of Small Nematodes._--Mix the fæces thoroughly with water. Allow to settle for five minutes. Carefully decant off, or better, syphon off the fluid. Mix the sediment again with water. Allow to settle. Remove the fluid. Repeat several times. Examine the sediment in a Petri dish. As the fluid is poured off, the worms will be seen collected in the backwater. Remove them with a brush. Fix in hot 70 per cent. alcohol.

CULTIVATION OF LARVAL FORMS OF ANCYLOSTOMA AND STRONGYLOIDES.

A modification of the second method of Looss (p. 455) is that of Fülleborn. A glass filter funnel is lined with linen or with cotton wool dyed black with iron-tannin. On this is placed a layer of sterile sand, and on top of this the fæces. The whole is moistened. The larvæ hatch out and wander through the meshes of the wool, appearing on the edges of the same as white threads visible to the naked eye. With a platinum needle these can be easily removed. The glass filter can be placed on a glass cylinder, and this in another large stoppered cylinder containing caustic potash solution at the bottom, so that any larvæ escaping from the funnel are killed.

D. *ACANTHOCEPHALA*, Rud.

Gutless, nematode-like worms that carry at their anterior end a
retractile rostrum beset with hooks. In their adult condition they
only live in vertebrate animals. During their larval stage they are
often parasitic in invertebrate animals.

The _Acanthocephala_ are elongated cylindrical worms, with a
rounded posterior end. In some species an annulation is distinctly
recognizable; they are, however, not segmented. The size varies
according to the species, between about 5 to 10 mm. and 40 to 50 cm.;
in general, however, there is a preponderance of the small species.
The sexes are separate, and the males can easily be distinguished
from the females without examination of the genitalia, as the females
are both larger and thicker.

The body wall of Echinorhynchus is limited by a thin cuticle, which
is attached inwardly to the hypodermis. In only exceptional cases
a syncytium with large nuclei, even in the adult condition, is
represented by the hypodermis; and in it fibre systems, the elements
of which run in layers in various directions, appear, and it is only
towards the interior from these strata of fibres that the nuclei of
the hypodermis are found. As a rule, these fibres, at all events
the radiary fibres, are regarded as muscles. Hamann describes them
as elastic fibres, which lie in a viscid gelatinous connective
substance (transformed protoplasm?); a lacune system filled with
a granular fluid, the central part of which are two longitudinal
lacunes lying at the sides, also belongs to the cutaneous strata, as
do the so-called lemnisci, two short, flat organs suspended in the
body cavity, and the pedicles of which are attached anteriorly at the
border between the rostrum and body; their structure as well as their
origin permit them to be traced to the skin (fig. 348A).

Finally, inwardly below the skin there follows a layer of annular,
and after these a layer of longitudinal muscles, the structure
cells of which remain present in the residues, carrying nuclei. The
motor apparatus of the rostrum, the sheath of the rostrum, and the
lemnisci also belong to the muscular system. The rostrum represents a
finger-shaped hollow process of the cutaneous layer; but, according
to Hamann, it originates from the entoderm and passes through the
skin secondarily. It is covered by a thin cuticle, and as a rule
contains a large number of regularly placed chitinous hooks that
adjoin a granular formation tissue. From the base of the rostrum
springs a tubular hollow muscle extending into the body cavity; this
is the RECEPTACULUM PROBOSCIDIS, from the base of which again bundles
of longitudinal muscles originate, which pass along its axis and
that of the rostrum itself, and are inserted at the inner surface of
its anterior end (RETRACTOR PROBOSCIDIS). These muscles when they
contract invaginate the proboscis and draw it into the receptaculum;
when reversed they act again as PROTRUSOR PROBOSCIDIS. The whole of
the anterior body, however, can be invaginated, and for this purpose
there is a muscle that originates from the body wall at a variable
distance back, and which is joined to the receptaculum (RETRACTOR
RECEPTACULI); there is also a bell-shaped muscle which springs from
the body wall behind the lemnisci in rings, and passes forward to the
spot of attachment of the lemnisci.

The nervous system consists of a cluster of ganglia situated at the
base of the rostrum, from which three nerves pass towards the front
and two towards the back. No sensory organs are known.

The excretory organs, according to Kaiser, lie at the upper border of
the ductus ejaculatorius in the male and at the so-called bell in the
female. Here they represent the long-known villous tufts, placed on
disc-like cushions. In each of the cylindrical villi--which terminate
blindly towards the body cavity--there lies a cilium, which springs
from the membrane lining the villus, and which lies in a space cavity
of the villus, which ultimately proceeds as a little canal. There are
three canals discharging into the uterus that serve to conduct the
excretory materials from the body cavity; special glandular cells
corresponding to the terminal cells of the Platyhelminths, at the
commencement of the system, are not present in the Acanthocephala.

SEXUAL ORGANS.

(_a_) _Male Organs._--The greatest part of the male genital apparatus
is contained in a muscular sheath--the ligament--which originates
at the posterior end of the receptaculum proboscidis, passes along
longitudinally through the body cavity, and is inserted at the
posterior end of the worm. The two oval testicles usually lie one
behind the other; their vasa efferentia unite sooner or later into a
vas deferens which passes backwards, and finally terminates in the
penis; the terminal portion of the conducting apparatus is surrounded
by six large glandular cells (prostatic glands) the excretory ducts
of which open into the vas deferens. The penis itself is placed at
the base of a bell-shaped invagination of the posterior end, the
bursa, which is everted during copulation.

(_b_) _Female Organs._--There are only two ovaries present in the
ligament during the larval stage. During the course of growth they
divide into accumulations of cells (placentulæ, loose or floating
ovaries), which finally cause the ligament to burst and they thus
attain the body cavity. Thence a peculiarly constructed apparatus
finally conveys the eggs out. This apparatus consists of the uterine
bell and vagina, the latter discharging at the posterior extremity
of the body. The bell is a muscular canal provided with apertures at
both the anterior and posterior extremities. Its interior space is in
direct communication with the body cavity, and the anterior orifice
takes up all materials floating in the cavity--egg-balls, mature and
immature eggs--and pushes these further backwards. The continuation
of the bell lumen is now narrowed by a number of large cells in such
a manner that only bodies of a certain form can pass through this
tract and attain the uterus; everything else is conveyed back into
the body cavity through the posterior opening of the bell.

The eggs are already fertilized in the body cavity, and in this
position go through their development to the formation of the embryo.
Completely developed eggs are surrounded by three shells, and are
generally fusiform. The eggs agglomerate in masses in the uterus
until they are finally deposited through the vagina and vulva.
For the further development, the transmission of the eggs into an
intermediary host--usually a crustacean or an insect--is necessary;
the metamorphosis is very complicated; but this transmission may be
very easily effected artificially by feeding suitable crustaceans
(_Asellus_, _Gammarus_, etc.) with the eggs of _Acanthocephala_; this
being the only method of inducing the larva to hatch out so that
its structure may be studied. The larva appears in the form of an
elongated, somewhat bent body, at the stumpy anterior end of which
there is a crown of hooks or spines, whereas the posterior end is
pointed. Especial retractors draw in the hook-beset anterior surface,
and an elastic cushion beneath them jerks them forward again when
required. In the middle of the body a roundish heap of small cells is
seen, from which the entire body of the Echinorhynchus originates,
even to the cutaneous layer; the latter is also the larval skin in
which the small Echinorhynchus gradually grows. The development of
all the organs takes place within the intermediary host, and the
parasite only needs to be imported into the terminal host to attain
the adult stage after a certain growth. In some cases, however, a
second intermediary host is utilized.

Species of _Acanthocephala_ only occur exceptionally in human beings.

*Echinorhynchus gigas*, Goeze, 1782.

Syn.: _Tænia hirudinacea_, Pallas, 1781.

The body is elongated, gradually decreasing in thickness towards the
back. The rostrum is almost spherical, and is beset with five or six
rows of recurved hooks. The males measure 10 to 15 cm. in length,
the females 30 to 50 cm.; the eggs are provided with three shells,
of which the middle one is the thickest. The eggs measure 0·08 to
0.1 mm. in length. The GIANT ECHINORHYNCHUS occurs especially in the
intestinal canal of the domestic pig; it is less common in other
mammals. It bores deep into the mucous membrane with its rostrum,
and causes an annular proliferation around the perforated spot;
occasionally also it causes perforation of the intestine.

It is doubtful whether the giant Echinorhynchus occurs in man.
Leuckart admitted that there were a few positive cases. According
to Lindemann, _Ech. gigas_ occurs in human beings in South Russia,
and its presence is not rare. This statement, however, has not been
confirmed. Its presence in man is by no means impossible, as its
intermediary host, the cankerworm, or cock-chafer (_Melolontha_),
is, according to Schneider, occasionally eaten raw by human
beings. According to Kaiser, the golden beetle (_Cetonia aurata_)
and, according to Stiles, another beetle in America (_Lachnosterna
arcuata_) are also intermediary hosts.

*Echinorhynchus hominis*, Lambl, 1859.

This term is applied to an ECHINORHYNCHUS found by Lambl in the
intestine of a boy who had died of _leucæmia_; the worm was 5·6 mm.
in length, and the almost spherical head was beset with twelve
transverse rows of hooks.

*Echinorhynchus moniliformis*, Bremser, 1819.

The male is 4 cm. in length, the female 8 cm. long. This species
lives in the intestine of field-mice, rats, marmots and _Myoxus
quercinius_. A beetle (_Blaps mucronata_) is the intermediary host.

This species has also once been artificially cultivated in man
(Grassi and Calandruccio).

E. *GORDIIDAE.*

Very long thin worms similar to Filariæ, which, in their adult
condition, live free in brooks, pools and springs; the mouth and the
commencement of the intestine are obliterated; there are no lateral
ridges, and the muscular system presents a structure different to
that of the _Nematoda_. The posterior end of the male is split, and
spicules are lacking; there are two testicles. In both sexes the
genitalia discharge through the terminal gut.

The larvæ, which carry a rostrum beset with hooks, force themselves
into the larvæ of water-insects; more rarely they invade molluscs,
and they then become encysted within the body of the host. According
to Villot, at least a part of them attain the intestine of fishes,
where they again become encysted, and after a period of rest they
travel into the tissues of their hosts, and finally again reach the
exterior by way of the intestine, where they then become adult. In
most cases, however, the gordius larvæ are taken up by predacious
water insects; they live for a while in the body cavity of these
insects, undergo a metamorphosis, and finally wander into the water.

A few species invade man accidentally with water, in which case they
are usually vomited up:--

_Gordius aquaticus_, Dujardin, 30 to 90 cm. in length (Aldrovandi,
Degland, Siebold, Patruban).

_Gordius tolosanus_, Duj., 11 to 13 cm. in length (Fiori).

_Gordius varius_, Leidy, 10 to 16 cm., female, up to 30 cm. in length
(Diesing).

_Gordius chilensis_, Blanch. (Guy). _Gordius villoti_, Rosa
(Bercutti, Camerano); _Gordius tricuspidatus_, L. Def. (R.
Blanchard), _Gordius violaceus_, Baird (Topsent), and _Gordius
pustulosus_, Baird (Parona).

F. *HIRUDINEA s. DISCOPHORA* (Leech).

The _Hirudinea_, which have been appropriately included amongst the
Annelida, differ in many respects from the typical members of the
group; their body is long and flat, it lacks the parapodia that
are characteristic to all forms of Annelida; but, on the other
hand, possesses a terminal posterior sucker, and in many species
there is also an anterior sucker. The mouth is terminal at the
anterior end, the anus lies dorsally above the posterior sucker
(fig. 348D). The body is segmented, but this is less manifest in
the body covering than it is in the arrangement of the internal
organs; the segmentation, nevertheless, is also indicated exteriorly
by the appearance of the cutaneous sensory organs which correspond
to the segments. This shows what the condition of the ganglia in
the abdominal ganglion chain has taught us, that the anterior and
the most posterior segments are considerably abbreviated--a part of
the latter taking part in the formation of the suctorial organs.
In a great many species the skin is distinctly annulated, four or
five of such rings, at least in the central region of the body,
appearing on one segment of the body. The condition of their body
cavity is another peculiarity of the _Hirudinea_; it is narrowed by
the powerful development of the connective tissue and the muscular
system into four tubular sinuses, which have the appearance of
blood-vessels. There are usually one dorsal and one ventral median
trunks, as well as two lateral trunks; in addition, a particular
blood-vessel system exists.

The skin consists of a very thin cuticle that is cast off from time
to time; it is secreted by the underlying cylindrical epithelium,
which contains numerous goblet cells. The muscular system is
strongly developed; it consists of long tubular fibres, which run
circularly, longitudinally and in the dorso-ventral direction; the
muscular system is subject to a particular expansion in the clinging
organs and at the commencement of the intestine. On the whole, the
alimentary canal represents a tube running straight from the mouth to
the anus, which possesses a number of blind sac-like protuberances
at the sides varying according to the species. The most anterior
section, the pharynx, in the leeches with maxillæ carries three
chitinous, semicircular plates furnished with teeth--the jaws--which
serve to tear up the epidermis in order to open the blood-vessels;
in the leeches with rostra a long protractile proboscis rises from
the base of the elongated pharynx. Numerous salivary glands, the
secretion from which possesses toxic properties, discharge into
the pharynx. The œsophagus, which follows the pharynx, and to the
exterior of which numerous radiary muscles are fixed, is a suctorial
organ in its entire structure. The nutriment in the larger species
consists of the blood of vertebrate animals, in smaller species and
in the young stages the food consists of small invertebrate animals.

The NERVOUS SYSTEM exhibits the typical structure of other segmented
worms; the sensory organs consist of the previously mentioned
goblet-shaped cutaneous sensory organs, of the organs of taste, and
of eyes, the latter frequently being present in large numbers.

The EXCRETORY or segmental organs exhibit many peculiarities, which
cannot, however, be detailed here. They commence with funnels in the
lacunes of the body cavity, and usually discharge on the ventral
surface.

Almost all the _Hirudinea_ are hermaphrodite and copulate
reciprocally. The two ovaries are very small, and the oviducts that
proceed from them soon unite into a common duct, which then passes
into the uterus and discharges through the short vagina in the
median line of the ventral surface behind the male organs into the
so-called clitellar region. The male sexual apparatus consists of
symmetrically arranged testicles, varying in number according to the
species, the short vasa efferentia of which, one by one, run into the
vas deferens, passing towards the front on each side. In front, at
about the level, or a little in front, of the female genitalia, the
two vessels pass into a convoluted mass of tubes to the so-called
epididymis, and then discharge into the single protractile penis
(fig. 348D).

All leeches deposit so-called COCOONS. These are small barrel-shaped
or pouch-like bodies, which are surrounded by a thicker shell and
contain a number of eggs in a large mass of albumen; the albumen
originates from glands of the generative organs, the shell substance
from cutaneous glands of the clitellar region.

Family. *Gnathobdellidæ* (Leeches with Jaws).

These are distinguished by the possession of usually three jaws in
the pharynx; the body consists of twenty-six segments. The posterior
sucker is large and flat; the anterior sucker is smaller. The
_Hirudinea_ have five pairs of eyes, the _Nephelinæ_ have four pairs.

Genus. *Hirudo*, L., 1758.

The entire body consists of 102 annulations, five appearing on one
segment in the central region of the body. The pharynx has three
semicircular jaws, the arched border of which is beset with numerous
teeth (50 to 100). The male sexual orifice lies between the thirtieth
and thirty-first rings, the female orifice between the thirty-fifth
and thirty-sixth. There are numerous species, some of which are
utilized for medicinal purposes.

*Hirudo medicinalis*, L., 1758.

It occurs in numerous colour varieties, one of which has been
designated _Hirudo officinalis_, Moq.-Tandon. Usually the dorsal
surface is greyish-green and is marked with six rusty-red
longitudinal stripes. The ventral surface is olive-green, more
or less spotted with black, and marked at the sides with a black
longitudinal line. The length averages 8 to 12 to 20 cm. This leech
lives in swamps, ponds and brooks, overgrown with plants and having
a muddy bed. The cocoons are deposited in the soil at the sides.
Europe, as well as North Africa, is its home. At the present day it
has been exterminated from most parts of Central Europe, but it is
still very common in Hungary. Its use for medicinal purposes is well
known. A large leech can suck about 15 grs. of blood, and about the
same amount is lost through secondary hæmorrhage.

*Hirudo troctina*, Johnston, 1816.

Syn.: _Hirudo interrupta_, Moq.-Tandon, 1826.

This species measures 8 to 10 cm. in length. The back is greenish,
with six rows of black spots surrounded by red; the lateral borders
are orange-coloured; the abdomen spotted or unspotted. Its habitat is
in North Africa and Sardinia. It is applied medicinally in England,
Spain, France, Algeria, etc.

Genus. *Limnatis*, Moq.-Tandon, 1826.

Nearly related to Hirudo, but is differentiated by a longitudinal
groove on the inner surface of the upper lip of the anterior sucker.
The jaws are furnished with over 100 very sharp toothlets.

*Limnatis nilotica*, Savigny, 1820.

Syn.: _Bdella nilotica_, Sav.; _L. nilotica_, Moq.-Tandon; _Hæmopis_
(_vorax_), Moq.-Tandon, 1826, _p. p._; _Hæmopis sanguisuga_,
Moq.-Tandon, 1846 (_nec Hir. sanguis_, Bergm., 1757).

This species measures 8 to 10 cm. in length, and becomes gradually
more pointed towards the front; the body is always soft. The back is
brown or greenish, and has usually six longitudinal rows (rarely only
two or four) of black dots. The abdomen is dark; but numerous colour
variations occur.

The native place is North Africa, especially the coastal regions; it
is also found in the Canaries, the Azores, Syria, Armenia, Turkestan,
perhaps also Southern Europe. It is taken into the mouth with
drinking water, and may settle in the pharynx, larynx, œsophagus, and
nasal cavities of human beings. This species has also been observed
in the vagina and on the conjunctiva. It is equally fond of attacking
domestic animals.

_Hirudo mysomelas_ (Senegambia) and _Hirudo granulosa_ (India) are
placed with this genus, and, like our leech, are also used for
medicinal purposes.

Genus. *Hæmadipsa*, Tennent, 1861.

These leeches live on land, and measure 2 to 3 cm. in length. About a
dozen species are known. They are a veritable scourge to persons in
the tropics (Asia, South America), as they attack them to suck their
blood. They are able to force their way even under close-fitting
garments, so that it is difficult to protect oneself from their
assaults (_Hæmadipsa ceylonica_, Bl., and other species).

Family. *Rhynchobdellidæ* (Leeches with Rostrum).

These are furnished with a proboscis in lieu of the jaws; the segment
consists of three annulations.

Genus. *Hæmentaria*, de Filippi, 1849.

*Hæmentaria officinalis*, de Fil.

Inhabit Mexico, where they are used for medicinal purposes.

Genus. *Placobdella*, R. Blanch.

*Placobdella catenigera*, Moq.-Tandon.

Indigenous to South Russia, Hungary, Italy and South France. It is a
parasite of the swamp turtle, but frequently attacks human beings.

G. *ARTHROPODA* (Jointed-limbed Animals).

BY

FRED. V. THEOBALD, M.A.

BILATERALLY symmetrical segmented animals which are covered with a
thick cuticle that is frequently calcareous (_Crustacea_), but always
thinner between the segments; they carry (primitively) a pair of
jointed appendages on every segment.[321] The segments of the body
are uniform in certain regions, but differ from those of contiguous
regions, so that it is easy to distinguish three parts (head, thorax
and abdomen), each composed of segments. The cephalic segments are
always formed into a uniform head, the segmentation being scarcely
recognizable at either end; the thoracic segments may also fuse, or
part or all of them may coalesce with the head; the abdomen, as a
rule, retains its segmentation, but this may possibly also be lost,
in which case it is [sometimes] united to the cephalothorax. The
structure of the three regions depends mostly on the varying form
and function of the appendages: those on the head are primitively
locomotive organs (and frequently are still so in the early stages),
but they become transformed into feelers and mouth-parts (mandibles,
maxillæ); the limbs of the thorax, however, usually retain their
ambulatory functions, as frequently do those of the abdomen;
sometimes, however, the abdominal limbs disappear, entirely or
partly; in the latter case they are then utilized for other purposes.

[321] [In most _Arthropoda_ the skin is hardened by a deposit of chitin (_Hexapoda_, etc.).--F. V. T.]

In their organization the _Arthropoda_ approach the segmented worms.

The _Arthropoda_ are generally divided into five groups
(_Crustacea_,[322] _Protracheata_, _Arachnoidea_, _Myriapoda_,[323]
and _Insecta_ or _Hexapoda_), of which only the _Arachnoidea_ and the
_Hexapoda_ interest us here.

[322] Parasitic or free-living Crustaceans may now and then invade man abnormally. Thus, according to Betten, _Caligus curtus_ invade the cornea (Betten, R. A., “Par. Crust. as a Foreign Body on the Cornea,” _Lancet_, 1900, i, p. 1002; and _Centralbl. f. Bakt. u. Par._, xxix, p. 506). According to Laboulbène, also _Gammarus pulex_ (Laboulbène, A., “Obs. d’accid. caus. par le _G. pul._ apport. avec l’eau de boison dans l’estomac d’un homme,” _Bull. Acad. méd._, 1898, p. 21).

[323] R. Blanchard has compiled thirty-five cases in which _Myriapoda_ have been observed in the intestine as well as in the nose of human beings (“Sur le pseudopar. d. myriap. chez l’homme,” _Arch. de Par._, 1898, i, p. 452). E. Munoz Ramos reports an additional case (_ibid._, p. 491). A few years ago a doctor in East Prussia sent me a rain worm out of a lady’s nose (_cf._ Hanau, A., “Wahrsch. Pseudo-paras. v. Schmeissfliegenlarv. u. angebl. Paras. v. Regenwürmern b. einer Hysterischen,” _Arch. de Par._, 1899, ii, p. 23).

_A._ *ARACHNOIDEA* (Spiders, Mites, etc.).

The head and thorax are always united together; the abdomen is either segmented or without exterior segmentation, in which case it is united with the cephalothorax.[324] The number of pairs of appendages amount to six, of which the two front pairs, the cheliceræ and the pedipalpi, are attached to the head region and the four remaining pairs to the thoracic region.[325] The abdomen in the adult condition has no appendages. The Arachnoids are air-breathers, and for this purpose are either provided with tracheæ or with so-called lung-sacs, or they breathe through the surface of the body. Some aquatic forms breathe by gills.

[324] [This is only so in the _Acarina_ or mites, not in the _Araneida_ or spiders.--F. V. T.]

[325] [The true character of the _Arachnoidea_ is the presence of four pairs of ambulatory appendages. This number is reduced to two pairs in the gall-making _Phytoptidæ_, and they differ from all other _Arthropoda_ in having no antennæ.--F. V. T.]

There are eight or ten orders of Arachnoids,[326] of which, however, only two, the _Acarina_ and the _Linguatulida_, have to be considered here.[327]

[326] Twelve orders are now recognized, as follows: _Pentastomida_ or Linguatulids; _Tardigrada_ or bear-animalcules; _Phalangidæ_ or harvest-men; _Acarina_ or ticks and mites; _Palpigradi_; _Solifugæ_; _Pseudoscorpionidea_ or book mites; _Pedipalpi_ or false scorpions; _Scorpionidea_ or true scorpions; _Araneida_ or spiders; _Xiphosura_ or king crabs; and _Pycnogonida_, marine Arachnoids.

[327] _Chelifer cancroides_ has also been observed as a pseudoparasite in man (Arnault de Very, S., “Pseudopar. du. _Chel. cancr._ chez l’homme,” _Compt. rend. Soc. de Biol._, 1901, liii, p. 105).

Order. *Acarina* (Mites).

Small Arachnoids, the three parts of the body of which are, as a
rule, coalesced; it is only rarely that a faint line indicates the
division between a cephalothorax and abdomen. The two appendages
on the head are designed for biting or puncturing and sucking, and
vary according to their use. The cheliceræ[328] are fang-like jaws
or puncturing bristles forming a kind of rostrum, the pedipalpi are
claw-like or shear-shaped, or form a suctorial proboscis.[329] The
four pairs of legs are usually well developed, more rarely they
are rudimentary or have partly vanished; many parasitic forms are
provided with pedunculated suckers [ambulacra--F. V. T.]. Respiratory
organs (tracheal tufts) may be present or absent. The nervous system
is reduced to a minimum, eyes are usually lacking. The intestine,
situated in the central part, generally has three blind appendages;
the anus is situated on the venter above the posterior end. Sexes
separated; nearly all the species deposit eggs, from which six-legged
larvæ hatch. The _Acarina_ live either free in the water or in moist
soil, or they are parasitic on plants and animals.[330]

[328] [The cheliceræ are sometimes regarded as modified antennæ, but it is more natural to regard them as the morphological equivalent of the mandibles of _Hexapoda_.--F. V. T.]

[329] [The pedipalpi, or second pair of jaws, consist of a stout basal segment and a palp, which may have the appearance of a leg in _Arachnida_; this may end with or without a claw, or with a chela (scorpions); they may also form a tube enclosing the styliform cheliceræ (mites).--F. V. T.]

[330] [_Acarina_ are also found living upon trees, feeding upon other Arthropods and also upon spores of lichen and fungi (_Oribatidæ_ or beetle mites); they also swarm indoors amongst stores and provisions (_Tyroglyphidæ_ and _Glyciphagi_, household, sugar and cheese mites). This order is very important, as many are parasites upon man, his domestic animals and his cultivated plants, and attack his provisions and stores. Some live on blood, and in some of the ticks distribute various protozoal and other blood parasites and germs.--F. V. T.]

Family. *Trombidiidæ* (Running Mites).

Soft-skinned _Acarina_ with tracheæ and with two eyes, usually
pedunculated; they are often brightly coloured; cheliceræ lancet- or
claw-shaped; pedipalpi claw-like; legs composed of six segments, with
suctorial discs between the terminal ungues.[331] Larvæ six-legged.
To the latter belong the larvæ of several species of Trombidium such
as:--

[331] [Some have seven segments to the legs.--F. V. T.]

Genus. *Trombidium*, Latreille (and *Leptus*).

*Leptus autumnalis*, Shaw, 1790.

Leptus occur as parasites in the human skin and cause a cutaneous disease known as autumn erythema, and produce a very unpleasant sensation on account of the troublesome itching; in children it is very often accompanied by fever.[332]

[332] [This minute parasite is especially obnoxious in barley fields. In walking over barley stubble one is sure to be attacked by this Acarus in many districts. Trombidium is often very prevalent in gardens, especially along rows of peas, and in spring they may be found on fruit trees and bushes. Nut-pickers are frequently attacked by Leptus, and also pickers in other fruit plantations. It is often called the harvest mite.--F. V. T.]

Formerly these mites were considered adult forms, but when they were
recognized as mite larvæ they were taken for those of the spider-mite
(_Tetranychus telarius_); the investigations of Hanstein, however,
showed this to be a mistake. When Henking first investigated the
development of _Trombidium fuliginosum_, parasitic in the larval
stage on vine-fretters, he demonstrated the occurrence of a form
very similar to _Leptus autumnalis_, and the “autumn, grass, or
gooseberry” louse was commonly designated the Trombidium larva. Even
before Henking’s work it had been described by Mégnin as the larva
of _Trombidium holosericeum_, a red-coloured species, frequently
occurring in spring and summer on the ground, trees, etc. This
assumption, however, as Moniez was the first to explain, is not
correct; indeed, as many as three species come under consideration:
_T. gymnopterosum_, L., _T. fuliginosum_, Herm. (according to
Brucker), and two species known hitherto only in the early stage, _T.
striaticeps_, Helm. et Oudem., and _T. poriceps_, Helm. et Oudem.,
which are not only parasitic on mammals, but on birds, on Arthropods
and especially on insects. Arthropods appear to be the normal hosts
for the larvæ.

The above-mentioned forms invade the skin of man by means of their oral apparatus, by preference invading the orifices of the sebaceous glands so as to suck the blood; around the point attacked there arises a wheal about the size of a lentil, and around the inserted hypopharynx a fibrinous secretion, the “proboscis,” which, however, is a product of the host, just as chitinous secretions are provoked by Trombidia parasitic on Arthropods.

Further species, analogous in habit to _Leptus autumnalis_, are
described by Riley from Central and South America as _L. americanus_
and _L. irritans_.

[_L. autumnalis_ attacks small mammals by preference, such as moles and hares, which are often literally covered with them. Dogs are also subject to their attack, and cats suffer similarly. This mite also frequently appears in colonies on cows; cavalry horses after autumn manœuvres often suffer from an erythematous affection about the hocks and knees due to this pest.

[A number of Leptus, so far undescribed, occur abroad which attack man in the same way as _L. autumnalis_ in Europe. Dr. Durham has brought me specimens from British Guiana called _bête rouge_; this species works under the skin much as does our European species, but it is very distinct, being considerably larger.--F. V. T.]

*Trombidium tlalsahuate*, Lemaire, 1867.

_T. tlalsahuate_ occurs in Mexico under conditions similar to those of Leptus here. It also frequently attacks men, and especially fastens itself on to the eyelids, in the axillae, navel, or on the prepuce; it induces itching and swelling of the parts affected, and sometimes even causes suppuration; the symptoms, however, generally disappear after a week and remain localized.[333]

[333] Lemaire, “Import. en France du tlalsahuate,” _Compt. rend. Acad. Sci._, Paris, 1867, lxv, p. 215.

Other species of mites which attack man are reported, mostly by travellers, from various other places; zoologically, however, there is little known about them. The pou d’agouti in Guiana, niaibi in New Granada, colorada in Cuba, mouqui in Para, and the buschmucker in New Guinea represent a few of these.

*Akamushi* or *Kedani*.

In a few districts of Japan there occurs a serious illness, with a mortality of 40 to 70 per cent. It is called river or flood fever, and the Japanese doctors have connected it with a small mite (akamushi, kedani). Baelz has opposed this opinion on the grounds that he has repeatedly observed the same species of mite in his dwelling without any subsequent illness occurring. According to Keïsuke Tanaka, however, a connection certainly does exist, inasmuch as the akamushi, like Leptus, attacks persons to suck blood. If the mite is not removed, or if the spot attacked is injured by scratching, etc., a papule surrounded by a red area forms, and a pustule ensues; and finally a black scab covers the seat of injury. The lesion becomes the point of entrance of bacteria, especially a species of _proteus_ which produces river fever. If the mites are carefully removed no general illness takes place.

The orange-red mites, which we only know in their larval condition, measure 0·16 to 0·38 mm. in length by 0·10 to 0·24 mm. in breadth. They have leg-like palpi with three joints, hirsute bodies, and very hairy legs composed of five segments, terminating with three ungues.

Family. *Tetranychidæ* (Spinning Mites).

These have tracheæ and eyes; the palpi are composed of four segments,
of which the last but one has a powerful claw. The legs have six
segments with sucker discs between the claws.

[The red spiders or spinning mites (Tetranychi) are usually placed in the family _Trombidiidæ_.--F. V. T.]

Genus. *Tetranychus*, Dufour.

*Tetranychus molestissimus*, Weyenbergh, 1886.[334]

[334] [This species is also known as _Bicho colorado_. It spins a web under the lower surface of the leaves, and it is only from December to February that it attacks warm-blooded animals and man.--F. V. T.]

Found in Argentine and Uruguay on the under surface of the leaves of _Xanthium macrocarpum_; it attacks mammals and men, producing severe itching, accompanied by fever in the latter.

It has been asserted by Haller that the CAPE AILMENT (Port Natal sickness) is caused by mites, but this statement has been contested.

*Tetranychus telarius*, L., 1758,[335] var. *russeolus*, Koch.

[335] [There is something wrong here, probably in the identification. _T. telarius_ is purely a plant-feeder, and it is extremely unlikely a variety would attack man. Anyhow, it will not do so in Great Britain.--F. V. T.]

This common spinning mite likewise attacks human beings, but the papules produced by it very soon disappear.

Family. *Tarsonemidæ.*

A family distinguished by complete sexual dimorphism, the species of
which are provided with tracheæ; the legs have five segments; the
terminal segments of the front pair of legs of both sexes possess a
claw; the terminal segment of the posterior pair of legs of the male
likewise has a claw. In the female this pair of legs, like the second
and third pairs of both sexes, is provided with two hooklets and a
sucking disc. The cuticle of the body on the back is “annulated.”

[This family of small transparent mites live normally as plant parasites. The last two pairs of legs are widely separated from the two front pairs.--F. V. T.]

Genus. *Pediculoides.*

*Pediculoides ventricosus*, Newport, 1850.

Syn.: _Heteropus ventricosus_, Newport, 1850; _Acarus tritici_,
Lagrèze-Fossot, 1851; _Physogaster larvarum_, Lichtenstein, 1868;
_Sphærogyna ventricosa_, Laboulbène and Mégnin, 1885.