Family. Physalopteridæ.
Genus. Physaloptera, Rudolphi, 1819.
Mouth surrounded by two large lateral lips bounded posteriorly by a cuticular band projecting anteriorly, forming a collar. Each lip bears anteriorly and inwardly a cuticular appendage, the external tooth. Immediately below and internal to the external teeth the internal teeth, one on each lip. Each lip bears two large submedian papillæ. Tail of male with four pairs of pedunculated papillæ in a row on each side external to the six pairs of unpedunculated papillæ. Spicules unequal. Vulva in the anterior region of the body. Eggs with a characteristic thick smooth shell.
Parasitic in the intestine, more especially the stomach, of mammals (twenty species), birds (twelve species), reptiles (fourteen species).
Physaloptera caucasica, v. Linstow, 1902.
The male measures 14·2 mm. in length and 0·71 mm. in breadth; the bursa is broad, rounded off in front and narrower at the back; the right spicule measures 0·62 mm. in length, the left spicule 1·76 mm.; there are two papillæ in front of the orifice of the cloaca, four behind it and six unpedunculated on the tail. The female measures 27 mm. in length, 1·14 mm. in breadth; the caudal extremity is rounded off; the vulva is on the border of the first and second sixth of the length of the body; the eggs have thick shells, and measure 57 µ by 39 µ. It has hitherto only been observed once, by Ménétriés in the intestine of man (Caucasus).
Fig. 339.—Bursa of Syngamus trachealis. a., anterior ray cleft; a.e., antero-external; m.a., antero-median; m.l., postero-median; p.e., postero-external; p., one branch of posterior (trifurcate). (Stephens.)
Physaloptera mordens, Leiper, 1907.
Large worms resembling an immature Ascaris lumbricoides.
The inner lancet-shaped teeth have a sharp cutting edge towards the lumen. Below each is a cuticular boss projecting into the mouth (fig. 340).
Male 30 to 50 mm., bursa with four pairs of pedunculated papillæ, the second and third lying external to the first and fourth on each side. Spicules unequal, one slender (4·6 mm.), the other stouter (6 mm.).
Female 40 to 55 mm. Tail sharp. Vulva opens between the anterior fourth and fifth of the body. Eggs 43·6 µ by 35·3 µ with a thick smooth shell.
Habitat.—Œsophagus, stomach, small intestine of man (several cases). Nyasaland and Portuguese East Africa.
Family. Ascaridæ, Cobbold, 1864.
Sub-family. Ascarinæ.
Without œsophageal or intestinal diverticula; spicules without flanges.
Genus. Ascaris, L., 1758.
Intermediate lips and auricles absent. Lips edged with fine teeth. Lips triangular in cross section. Not grooved on internal surface.
Fig. 340.—Physaloptera mordens, Leiper, 1907. (1) adult male: o.e., œsophagus; ch.i., chyle intestine; t.c., testicular coils; ves. sem., vesicula seminalis; sp. 1, long spicule; sp. 2, short spicule; B., bursa. (2) Mouth parts: c., cuticular collar embracing the two lips posteriorly; c.b., cuticular bosses guarding the mouth laterally; e.d., external tooth; i.d., internal tooth; sm.p., submedian papillæ. (3) egg of P. caucasica. (4) egg of P. mordens. (5) bursa enlarged: ped.p., pedunculated papillæ; ses.p., sessile papillæ. (After Leiper.)
Ascaris lumbricoides, L., 1758.
The colouring, in the fresh condition, is reddish-yellow or greyish-yellow; the body is of an elongated spindle shape. The oral papillæ are finely toothed. The dorsal papilla carries two sensory papillæ, the two ventral papillæ each one sensory papilla. The male measures from 15 to 17 to 25 cm. in length, and about 3 mm. in diameter; the posterior extremity is conical and bent hook-like ventrally; the spicules measure 2 mm. in length, are curved, and somewhat broadened at their free end; on each side around the orifice of the cloaca there are seventy to seventy-five papillæ, of which seven pairs are post-anal. The testicular tube is much folded, showing through the body integument, and is about eight times the length of the body. The female measures 20 to 25 to 40 cm. in length and about 5 mm. in diameter; the posterior extremity is conical and straight. The vulva is at the junction of the anterior and middle thirds of the body, which, at this point, has a slight ring-like constriction; the convoluted ovaries measure ten times the length of the body.
Fig. 341.—Ascaris lumbricoides. a, posterior extremity of the male with the spicules protruding from the orifice of the cloaca (Sp.); b, anterior extremity from the dorsal surface, the two lobes of the pulp of the lip separated by the “saddle”; c, anterior extremity from the ventral surface; P., excretory pore. (From Claus.)
The ova are elliptical with a thick (4 µ) transparent shell (fig. 342) and an external albuminous coating which forms protuberances; the ova measure 50 µ to 70 µ in length, 40 µ to 50 µ in breadth; they are deposited before segmentation; the albuminous coating is stained yellow by the colouring matter of the fæces, but is sometimes absent. The egg cell is unsegmented, it almost completely fills the shell, and its nucleus is concealed by the large amount of coarse yolk granules.
Abnormal or unfertilized eggs also occur in fæces. They are distinguished by their elongated form (80 µ by 45 µ), irregularly cylindrical, its contents consisting of refractive granules.
Ascaris lumbricoides is one of the most frequent parasites of man; it is distributed all over the inhabited parts of the world, and though it is particularly frequent in the warmer regions, yet it also occurs in Finland, Greenland, etc. In temperate climates A. lumbricoides occurs most frequently in young children; it is, moreover, more common amongst country dwellers than amongst the inhabitants of towns, but is not lacking in infants, adults and aged persons. As a rule only a few specimens are present in the intestine, but many cases are known in temperate zones in which several hundreds of worms have been found in the same patient. This species is particularly numerous in the negroes of Africa and America. It occurs also in the monkey, dog and pig (? A. suilla).
The parasite was known in ancient times; the Greeks called it ἐλμινς στρογγύλη, Plinius termed it Tinea rotunda, later on it was named Lumbricus teres. The ἄσκαρις of the Greeks is our Oxyuris.
The small intestine is the normal habitat of Ascaris lumbricoides; the worms, however, often leave this part of the intestine and wander into the stomach, whence they are frequently evacuated by vomiting, or they may creep through the œsophagus into the pharynx and crawl out through the nose or mouth; very rarely they may find their way into the Eustachian tube or into the naso-lachrymal duct, or into the excretory ducts of the liver and pancreas; exceptionally they may gain the trachea, and they have also been found in the abdominal cavity. They may bore through adhesions between the intestinal wall and the omentum (worm abscess); they occasionally penetrate the urinary apparatus and are passed with the urine; in febrile diseases A. lumbricoides usually leaves the intestine spontaneously. It is obvious that these wanderings may be accompanied by the most serious symptoms, but in sensitive persons the invasion of even only a few intestinal Ascarides gives rise to a series of almost inexplicable symptoms (hysterical, epileptiform attacks, cerebral congestion, aphonia, etc.), which cease with the expulsion of the worms, so that many authors are driven to the conclusion that these Ascarides secrete a toxin. Fortunately, the presence of A. lumbricoides in the intestine is easily demonstrated by the microscopical examination of the fæces.
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.
Fig. 346.—On the left, female; on the right, male. A, anus; M, mouth; V, vulva. Greatly enlarged. (After Claus.)
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.
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 CaCl2 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.
Fig. 348a.—The male of Echinorhynchus augustatus. L., lemnisci; T., testicles; P., prostatic glands; P.r., sheath of proboscis, with ganglion; R.r., retractor of sheath of proboscis. 25/1.
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.
Fig. 348b.—Anterior portion of the female apparatus of Echinorhynchus acus. On the left seen from behind, on the right seen from the front. F, inferior orifice of the bell; B, bell; Lig, ligament; M, mouth of bell; Ut, uterus. Magnified. (After Wagener.)
(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.