« AnteriorContinuar »
inch in length (fig. 1), of a milky white colour, with one end cut off obtusely and slightly puckered (the mouth), and the other
Fig. 1. pointed (the tail). Maw-worms exist in great numbers in the dog, chiefly occupying the large intestines, and not injuring the health to any great degree, unless they exist in very large numbers. They are male and female, and are propagated by ova.
The Round-worm (Ascaris lumbricoides) is from four to seven inches long, round, firm, and of a pale pink colour. The two extremities are exactly alike, and are slightly flattened in one direction at the point (see fig. 2), in which a shows the worm extended,
and b a group of three as actually discharged from the intestine of a dog in which they were thus knotted. I have often seen from six to a dozen round worms thus collected together, so as when discharged to form a solid mass as large as an egg. Like the last species they are propagated by ova, but sometimes these are hatched in the body of the parent, so that a large worm may be seen full of small ones. This species occasions much more inconvenience than the maw-worm, but still far less than the tape
Tape-worms in the dog are described by foreign writers as of five kinds, of which the Tenia solium and Bothriocephalus latus are common to man and the dog. The others 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, &c. The peculiarity in the bothriocephalus consists in the shape of the head (see fig. 4), which has two lateral longitudinal grooves (bothria), while that of the true tænia is bemispherical. The following is a description according to Professor Owen :—“The Tænia solium attains the length of several feet, extending sometimes from the mouth to the anus. The breadth varies from one-fourth of a line at its anterior part to three or four lines towards the posterior part of the body, which then again diminishes. The head (fig. 3, a) is small, and generally hemispherical, broader than long, and often as if 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 rugæ, 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 (6 b) are placed near the middle of one of the margins of each joint, and are generally alternate (fig. 5, c d). The Tenia solium is androgynous; that is to say, it produces its ora without the necessity for the contact of two individuals, the male and female organs being contained in each.” Professor Owen thus describes them : “In each joint of this worm there is a large branched ovarium (fig. 5, i), from which a duct (h) 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 colour, 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 perceived. 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
f Fig. 5.
diameters. A well-defined line (g), 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 segment, where it terminates in a small oval vesicle. This, as seen by transmitted light, is subtransparent in the centre, 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
passage outward.” (Cyclopedia of Anatomy, art. Entozoa.) 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 fæces, 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, depending partly upon the abstraction of nourishment, which is absorbed by the worm, and partly by the irritation produced by its presence in the intestines; and hence it is of the utmost importance to get rid of so troublesome a customer.
The Kidney-worm (Strongylus gigas) “inhabits the kidney of the dog, as well as that of the wolf, otter, raccoon, glutton, horse, and bull (see fig. 6). It is generally of a dark blood
F F 2