TAPEWORMS, OR CESTODES (Order Cestoda).

[Segmented Tapeworms (suborder Tomiosoma). Tapeworms without four retractile probosces (tribe Atrypanorhyncha). Tapeworms with four suckers (subtribe Tetrassichiona).]

Family TAENIIDAE.

In cattle and sheep we find both of the stages of tapeworms mentioned on page 21, namely:

FIG. 57.-Enlarged dorsal view of Gastrothylax crumenifer. (After Creplin, 1847, Pl. II, fig.

1.) See p. 67.

Larval forms (cystic worms, bladder worms, hydatids) which live in the muscles or parenchymatous organs, but not in the intestine. They render the meat unfit for food since they are transmissible (according to the species) to man and dogs; and— Adult worms (tapeworms, strobilae) which occur in the intestines of sheep and cattle (rarely in the ducts of the liver of sheep) and are not transmissible to carnivorous animals.

Hogs on the other hand appear to be infested only with larval tapeworms, although three isolated cases of adult tapeworms have been recorded for them. These three cases may have been accidental occurrences, the hogs having possibly become accidentally infested with worms which normally live in other animals.

m.

vp

a

FIG. 58. Enlarged ven. tral view of Gastrothylax crumenifer: a, acetabulum; up, opening to the ventral pouch. (After Creplin, 1847, Pl. II, fig. 2.) See p. 67.

Tapeworms of the family Taeniidae possess the following characters: The anterior extremity is represented by a more or less knob-like portion known as the head; this is followed by an unsegmented portion, the neck; head and neck extremity of Gas- together form the scolex; this in turn by the segments, or proglottids.

FIG. 59. Enlarged

view of anterior

trothylax crumeniThe head is provided with four cup-shaped suckers, which are fer: m, mouth; vp, never provided with hooks in any form known in cattle, sheep, opening to ventral or hogs, but are armed with numerous hookpouch. (After lets in some of the forms found in certain other Creplin, 1847, Pl. animals (man, rabbits, birds). The apex of II, fig. 4.) See p. 67. the head is provided with a muscular body, which develops into different forms in the various subfamilies. It may form a rostellum, which may be unarmed (Taenia saginata) or armed (Taenia solium). In the larval forms discussed in this paper (Taeniinae) the rostellum protrudes at the center of the apex, but in some other forms (Dipylidiinae) it may retract into a rostellum sac. In the adult tapeworms (Anoplocephalinae) of cattle, sheep, etc., the muscular body is composed of stellate fibers which move the suckers, but these fibers do not appear to form a true rostellum.

FIG. 60.-Enlarged

view of posterior extremity of Gastrothylax crumenifer. See p. 67.

The neck is very simple in structure, containing each side two longitudinal canals and a longitudinal nerve trunk. At the posterior portion of the neck, segments form by transverse division.

The segments increase in size, gradually becoming larger the farther they are from the head; reaching a maximum breadth, they decrease in width, and then increase in length more rapidly. The anterior segments are the youngest, the posterior seg

ments the oldest. Many zoologists look upon the entire tapeworm as a colony of animals, each separate segment representing a single individual, and all segments being descended from a single animal represented by the head

and neck.

Owing to their parasitic life, tapeworms are very degraded in their structure. The digestive tract is entirely absent, the worms taking their nourishment by osmosis through their entire surface. The nervous system is composed of nerve centers (ganglia), situated in the head, and two large lateral nerves, one of which extends on each side of the worm from the head to the posterior end of the strobila; in some cases, at

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ph

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ου.

Zc.

least, the lateral nerves
are connected by two
transverse nerves at the
distal end of each seg-
ment.

FIG. 61. Enlarged view of Gastrothylax crumenifer, with ventral pouch open: a, acetab. ulum; gp, genital pore; m, mouth. (After Creplin, 1847, Pl. II, fig. 5.) See p. 67.

The excretory system consists of two dorsal and two ventral longitudinal lateral canals, which are connected in various ways in the head; the ventral canals are connected by transverse canals at the posterior border of each segment. The genital organs form by far the most important organ system in the animal. In the first place, the entire genital system is repeated, so that each segment as it arrives at a given age possesses its own genital organs, independent of the organs of the other segments. Again, every segment is hermaphroditic, containing both male and female organs, and in some genera the segments are doubly hermaphroditic, containing double sets of male and of female organs. The male organs consist of a cirrus (penis), a cirrus pouch, a vas deferens, and numerous testicles. The female organs consist of a vulva, a vagina, an ovary, a vitellogene gland, a shell gland, oviducts, and a uterus. Each segment possesses one or two genital pores, the cirrus and the vulva of any given set of organs (except in the genus Amabilia, according to Diamare) opening at the same pore. In some species, so-called interproglottidal glands of unknown function are found between the segments. Life history.-Tapeworms pass through three stages of development, known as the oncosphere (or embryo), the larva (a bladder worm known as a cysticercus, a coenurus, an echinococcus, or a cysticercoid), and an adult form known as the strobila. A change of host is necessary for their development; the host in which the oncosphere develops into the larva is known as the intermediate host,

...ex.
a.

FIG. 62.-Dorsal view of Gastrothylax cru. menifer, magnified to show the anatomical characters: a, acetabulum; ex, terminal vesicle of excretory system; i, intestinal caeca; Lc, Laurer's canal; oe, oesophagus; ov, ovary; ph, pharynx; t, testicles; u, uterus; vd, vas deferens. X5. (After Otto, 1896, p. 96, fig. 3.) See p. 67.

FIG. 63.-Gastrothylax

Cobboldii, lateral view: a, acetabulum; i, intestine: m, mouth; rp, opening to ventral pouch. (After Poirier, 1883, Pl. II, fig. 3b. Taken from Braun, Vermes, Pl. XVIII, fig. 2.) See p. 67.

while the animal which harbors the adult form is known as the final host. The life history of Taenia saginata given on page 72 may be taken as typical for the family.

All of the larval cestodes of cattle, sheep, and swine belong to the subfamily Taeniinae, while all the adult forms found in these hosts are classified in the subfamily Anoplocephalinae.

Hard-shell Tapeworms (Cestodes of the Subfamily Taeniinae).

ph.
--g.

The Hard-shell Tapeworms, so called because of the thick striated eggshell (embryophore), are found as adults in the intestines of meateating mammals, while their larval stage is found in the muscles or parenchymatous organs of herbivorous and omnivorous animals. These larval forms are very important from the standpoint of meat inspection, and organs which harbor them should be excluded from the market or should be rendered wholesome before being placed on sale.

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The larval forms may be of three kinds, as follows:

(1) Cysticercus (figs. 68 and 76). This is the most simple form. The parasite consists of a cyst, which is invaginated at a given point. There is normally only one invagination to each cyst, and at the base of the invagination is situated the head of the future tapeworm. Besides the invagination, the cyst contains more or less liquid.

(2) Coenurus (figs. 99 and 100).-In this case there is a considerable number of invaginations, each containing a head.

(3) Echinococcus (fig. 105).-In the third type there is no invagination of the cyst wall, but brood capsules are formed from the parenchyma of the cyst and several heads are formed in each brood capsule.

FIG. 64.—Gastrothylax elon. gatum: g, ganglion; i, in testinal caeca; ph, pharyn geal bulb; t, testicle; u, uterus; vd, vas deferens Attempts have been made to subdivide the Taeniinae into (ductus ejaculatorius); ve, genera and subgenera, the genus Taenia Linnaeus being vasa efferentia; vg, vitelretained for the forms which possess a Cysticercus or a Coenulogene glands. (After Poirier, 1883, Pl. II, fig. rus as larval form, while Echinococcifer Weinland, 1861, has 26. Taken from Braun, been proposed as the generic name for Taenia echinococcus. Vermes, Pl. XVIII, fig. 7.) This generic division has not been accepted by the majority See p. 67. of helminthologists, most workers preferring to recognize only one genus, Taenia, but many authors admitting three subgenera, corresponding to the three types of larvae.

HARD-SHELL TAPEWORMS (Genus Taenia).

The following species of this genus must be considered in this report:

19. Beef Measles (Cysticercus bovis) of Cattle, and its adult stage, The Unarmed, or Beef Measle, Tapeworm (Taenia saginata) of Man.

[Figs. 68-74.]

LARVAL STAGE (Cysticercus bovis).

For anatomical characters, compare fig. 68 with key, p. 21.
SYNONYMY.-Cysticercus Taeniae saginatae Leuckart, 18-(?); C. bovis Cobbold,

1866; C. Taeniae mediocanellatae Knoch, 1868; C. inermis of various Germans and others, 18-(?); "Cysticerkus" bovis of Schneidemühl, 1896.

HOSTS.-Cattle, Rocky Mountain "antelope," llama, and giraffe. (See pp. 137-143.)

ADULT STAGE (Taenia saginata (Goeze, 1782)).

For anatomical characters, compare figs. 69-73 with key, p. 84. SYNONYMY (see also pp. 89-90).-Taenia solium Linnaeus, 1758, pro parte; T. cucurbitina Pallas, 1781, pro parte; T. cucurbitina Art [= var.] saginata Goeze, 1782; T. cucurbitina, grandis, saginata Goeze, 1782; T. solitaria Leske, (1785), pro parte; Halysis

solium (Linnaeus) Zeder, 1803, pro parte; Pentastoma coarctata Virey, 1823; "T. dentata" Nicolai, (1830) [nec Batsch, 1786]; "T. lata" Pruner, 1847 [nec Linnaeus, 1758]; Bothriocephalus tropicus Schmidtmüller, 1847; T. mediocanellata hominis, seu T. medio

paloniae, ventral view. (After Poirier, 1883, Pl. II, fig. 1a. Taken from

canellata seu T. zittaviensis Küchenmeister, 1852; T. solium var. mediocanellata (Küchenmeister) Diesing, 1854; Taeniarhynchus mediocanellata (Küchenmeister) Weinland, 1858; (?) Taenia solium var. abietina Weinland, 1858; T. inermis MoquinTandon, 1860; T. mediocancellata (--), date (?), see MoquinTandon, 1860; T. tropica (Schmidtmüller) Moquin-Tardon, 1860; T. megaloon Weinland, (1861); T. (Cystotaenia) mediocanellata of Leuckart, 1863; T. saginata (Goeze, 1782) of Leuckart, 1867; (?) T. abietina Weinland of Davaine, 1873; T. inermis Laboulbène, 1876; T. algérien, Redon, 1883; (?) T. solium var. minor Guzzardi Asmundo, 1885; T. algeriensis Braun, 1894 (=T. algérien Redon renamed).

ANOMALIES. (?) "Taenia vulgaris" Werner, 1782 [nec Linnaeus, 1758] T. dentata Batsch, 1786; (?) T. fenestrata Chiaje, 1833; T. capensis Moquin-Tandon, 1860; T. lophosoma Cobbold, 1866; T. fusa, T. continua, T. solium fusa seu continua Colin, 1876; T. mummificata Guzzardi Asmundo, 1885; T. nigra Davaine, 1877; T. inermis fenestrata Maggiora, 1891.

PRE-LINNAEAN NAMES.-Vermis cucurbitinus composing TaeFIG. 67.-Homalogaster nia longissima Plater, 1609; Lumbricus latus Movfetus, (1634); Taenia secunda Plateri Ernst, 1659; Lumbricus latus Tyson, 1683; Solium ou Ténia sans épine Andry, (1700); Taenia de la seconde espèce Andry, 1718; Taenia sans épine ou Taenia de la XVIII, fig. 3.) See p. première espèce Andry, 1741.

67.

BIBLIOGRAPHY.-For bibliography, see Huber (1892). For technical discussion, see Leuckart (1880, pp. 513-616); R. Blanchard (1886, pp. 315-382). HOST.-Man.

Life history.-Starting with the adult tapeworm (fig. 69) in the intes tine of man, the life history of the parasite, the knowledge of which we owe to Rudolf Leuckart, is as follows: The eggs (fig. 74) escape from the uterus and are passed with the excreta, or the segments containing eggs break loose from the tapeworm and either wander out of the intestine of their own accord or are passed with the excreta. In either case the eggs become scattered upon the ground or in water, and reach the cattle through their drinking water or with the fodder. When whole segments (generally several together) are passed, these crawl around on the ground or herbage, and cattle by swallowing them may become infected with numerous eggs at the same time. Upon arriving in the stomach, the eggshells are destroyed; the embryo then bores its