An elementary text-book of biology, comprising vegetable and animal morphology and physiology / by J.R. Ainsworth Davis.

  • James Richard Ainsworth-Davis
Date:
1893
Catalogue details

Licence: Public Domain Mark

Credit: An elementary text-book of biology, comprising vegetable and animal morphology and physiology / by J.R. Ainsworth Davis. Source: Wellcome Collection.

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    spines prevent the animal from slipping back as it makes its way along the bile-ducts of its host. The digestive and other organs are imbedded in a mass of tissue, which, since it supports the various parts and connects, them together, may be termed connective tissue. Polyhedrai nucleated cells are the main constituent of this tissue in the Liver-fluke, but there is also a certain amount of non-cellular o fibrous material between these. 2. Digestive Organs (Fig. 5).^—The mouth leads into a short tube which quickly forks, the two limbs of the fork passing back and giving off numerous branching processes, all of which end blindly. There is no anus. The oval mouth (0) is situated in the middle of the anterior sucker, and leads into a small mouth-cavity, which is followed by the oval, thick-walled ]phanj7ix that passes into a very short, straight, delicate tube, the gullet or resophagus, this again opening into a bifurcated intestine. Each half of this is a thin-walled, fairly wide tube (D), running back to the end of the body, and situated near the middle line. A number of small pouches project from its inner side, whilst a large number of pouches, mostly much branched, extend from its outer side to the edge of the body. Special muscles—i.e., bands of contractile fibres—are connected with the pharynx. A sheath of such fibres, the p^'otvactor muscle, closely surrounds this organ, and, on the other hand, is connected with the anterior sucker, while retractor muscles slant back from the pharynx to the dorsal wall of the body. Histology.—The pharynx is lined by a con- tinuation of the general cuticle. Its wall is very muscular, the fibres taking various directions. The gullet and intestine have very thin walls, consisting of an epithelial layer of cells, external to which is a structureless membrane. The term epithelium is applied to membranes, formed by one or more layers of cells, which cover external and line internal surfaces. The epithelium Fig. 5,—Distoma (from Claus after Leuchart) —Ali- mentary canal. O, Mont li, a short distance behind which is ventral sucker. D, right limb of intestine.
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