This section is from the book "The Dogs Of Great Britain, America, And Other Countries. Their Breeding, Training, and Management in Health and Disease", by John Henry Walsh (Stonehenge). Also available from Amazon: The Dogs Of Great Britain, America And Other Countries.
Tape-worms in the dog are of five kinds, of which the Tsrnia solium and Bothriocephalic latus are common to man and the dog. The other kinds are not readily distinguished from these two, and all are now said to be developed from the hydatid forms found in the livers of sheep, rabbits, etc. The peculiarity in the bothrioce-phalus consists in the shape of the head, which has two lateral longitudinal grooves, while that of the true taenia is hemispherical Professor Owen says: "The Tcsnia solium (Fig. 48) is several feet long. The breadth varies from one-fourth of a line at its anteiior part to three or four lines towards the posterior part of the body, which then again diminishes. The head (fig. 49) is small, and generally hemispherical, broader than long, and often as truncated anteriorly; the four mouths, or oscula, are situated on the anterior surface, and surround the central rostellum, which is very short, terminated by a minute apical papilla, and surrounded by a double circle of small recurved hooks. The segments of the neck, or anterior part of the body, are represented by transverse ruga, the marginal angles of which scarcely project beyond the lateral line. The succeeding segments are subquadrate, their length scarcely exceeding their breadth.
They then become sensibly longer, narrower anteriorly, thicker and broader at the posterior margin, which slightly overlaps the succeeding joint. The, last series of segments are sometimes twice or three times as long as they are broad. The generative orifices are placed near the middle of one of the margins of each joint, and generally alternate.
Fig. 48. - Tape-Worm.
Fig. 49. - Head Of Tape-Worm.
The Tarda solium is androgynous; that is to say, it produces its ova without the necessity for the contact of two individuals, the male and female organs being contained in each. Professot Owen further describes them: "In each joint of this worm there is a large branched ovarium, from which a duct is continued to the lateral opening. The ova are crowded in the ovary, and in those situated on the posterior segments of the body they generally present a brownish color, which renders the form of their receptacle sufficiently conspicuous. In segments which have been expelled separately, we have observed the ovary to be nearly empty; and it is in these that the male duct and gland are most easily per-ceived. For this purpose, it is only necessary to place the segment between two slips of glass, and view it by means of a simple lens, magnifying from 20 to 30 diameters. A well defined line, more slender and opaque than the oviduct, may then be traced, extending from the termination of the oviduct, at the lateral opening, to the middle of the joint, and inclined in a curved or slightly wavy line to near the middle of the posterior margin of the seg-ment, where it terminates in a small oval vesicle.
This, as seen by transmitted light, is sub transparent in the center, and opaque at the circumference, indicating its hollow or vesicular structure. The duct, or vas deferens, contains a grumous secretion; it is slightly dilated just before its termination. In this species therefore, the ova are impregnated on their passage outward'* From this minute description, it may be gathered that the ova are in enormous numbers, each section of the worm being capable of producing them to an almost indefinite extent; and as they are passed out of the body with the faeces, it is not surprising that they are readily communicated from one dog to another, as is almost proved to be the case from the fact of their prevalence in certain kennels, and absence from others. The injury caused by these worms is twofold, viz., the abstraction of nourishment, which is absorbed by the worms, and the irritation produced by their presence in the intestines. It is, therefore, of the utmost importance to get rid of so troublesome customers.