Page:Encyclopædia Britannica, Ninth Edition, v. 23.djvu/64

Rh towards the surface of organs, and sometimes a cure is effected spontaneously by its rupturing into the alimentary canal or into some other passage leading to the exterior. Cases in which the cyst opens into the blood-vessels are almost always suddenly fatal. . 3.—Various Forms of Tape-Worms. A, Tænia echinococcus; × 12 (from Leuckart). B, Archigetes sieboldi; × 60 (from Leuckart). C, Echinobothrium typus; × 10 (from Van Beneden). D, Caryophyllæus mutabilis; × about 5 (from Carus).

When the Echinococcus occurs near the surface of the body, it may be evacuated by puncture and a cure effected with but little risk.

The following classification of the Cestodes, based mainly on that of Van Beneden, exhibits the present state of our knowledge of the group:—

It seems advisable to add a few details regarding some of the forms alluded to in the above synopsis.

Amphilina foliacea, described as a Trematode by Rudolphi, is found in the body-cavity of the sturgeon. A number of unicellular glands open into the sucker, and are surrounded by the muscles of that organ; the nervous system consists of two ganglia, with a commissure, and two lateral nerves; the male organs resemble those of Bothriocephalus, the female those of the Trematodes; the family is generally regarded as furnishing a connecting link between the Cestoda and Trematoda; see Salensky (18) and Lang (7). . 4.—Bothriocephalidæ. A, A segment of Bothriocephalus latus, showing the generative organs from the ventral surface; ex., excretory vessels; c, cirrus; c.p., cirrus pouch; v.d., vas deferens; v.o. vaginal opening; v., vagina; sh.g., shell-gland; od., oviduct; ov., ovary; y.g., yolk-gland ; y.d., its duct; ut., uterus; u.o., uterine opening; the testes are not visible from this side; × 23 (from Sommer and Landois). B, C, marginal and lateral views of the anterior part of B. cordatus, showing the cephalic grooves; × 5 (from Leuckart). D, Ciliated embryo of B. latus; × 60 (from Leuckart).

Bothriocephalus latus (32) is the most conspicuous example of the family Pseudophyllidæ, and is, moreover, noteworthy as being the largest tape-worm found in man; its length often reaches 8 to 9 metres, and its extreme breadth 10 to 12 mm. The head bears two grooves, which correspond in position with the flat sides of the body. There are two (more correctly three) genital openings, which are situated, not on the margin but on the flat side of the body, on that surface which is usually called the ventral. The most anterior of these is the male aperture (fig. 4, A, c.), and immediately behind it is that of the vagina (v.o.), so close that on superficial examination the two often seem to coincide. This vaginal opening, like that of the Tæniadæ, serves for the intromission of the penis and for the fertilization of the ova, but not for the exit of the ripe eggs; this being provided for by a special aperture at the other end of the uterus from that at which the eggs enter it. This uterine opening (u.o.) is situated at a short distance behind the other two. The result of this arrangement is that the eggs can be evacuated without any injury to the proglottis, and consequently their discharge commences before its separation from the parent worm and may continue for a long period. The uterus (ut.) itself, owing to its disposition in folded coils, when full of eggs, presents an irregular, round, lobular appearance, which has been compared to a flower or heraldic lily. The yolk-gland (y.g.) is widely disseminated in the lateral areas of the segments, and its ducts (y.d.) form a series of branching tubules, first described by Eschricht (27) under the name “yellow ducts.” The excretory organs (ex.) differ from those of the Tæniadæ in that the canals exhibit a reticulate arrangement. The embryo (fig. 4, D) as it leaves the egg is covered with a ciliated mantle, which corresponds to the firm egg-shell and associated membrane of the cystic tape-worms, and perhaps also to the ciliated envelope of certain Trematode larvæ (see ). This ciliated organism swims freely about in the water, but after a time the six-hooked proscolex escapes from it. The next stage in its life-history is not yet known, but it has been recently shown by Braun of Dorpat (33) that at a subsequent stage it inhabits the pike and burbot, and develops into the sexual adult when transferred to the intestine of the human subject. The geographical distribution of Bothriocephalus is limited; it has been recorded with certainty in but few places outside Europe; while within that continent the coasts of the Baltic and Switzerland are